#include <iostream>
#include <algorithm>

using namespace std;

int main()
{
    int n, a;
    cin >> n >> a;

    if (n == 1)
        cout << 0 << endl;
    else
    {
        int S = n - 1;
        //int S = n;
        for (int i = 1; i <= n; i++)
        {
            S = S - min(a, i);

            if (S <= 0)
            {
                cout << i << endl;
                break;
            }
        }
    }
}

can anybody give me some tests?

I've seen few people got AC in 0.015 seconds, but how? I used binary search and each iteration's left border started from the last found number, but not from the beginning of array and got 0.031 seconds.

var a:integer;
    b:integer;
    va:integer;
    vb:integer;
    ea:integer;
    eb:integer;
    ra:integer;
    rb:integer;
    boxa:integer;
    boxb:integer;
begin
    readln(a,b);
    readln(va,vb);

    boxb:=b-(va-a);
    rb:=b-boxb;
    readln(ea,eb);
    boxa:=va-(eb-vb);

    writeln(a-boxa,' ',b-boxb);

end.

/*
My program got WA on test 11!!!
What's wrong with my code?
Anyone can help me!!!
*/
#include <map>
#include <set>
#include <ctime>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <vector>
#include <string>
#include <cstdlib>
#include <cstring>
#include <utility>
#include <iostream>
#include <algorithm>

#define FI            first
#define SE            second
#define LSON(x)            (x<<1)
#define RSON(x)            ((x<<1)|1)
#define Benefit(x,y)        x=max(x,y)
#define CS            const static
#define SORT_CMP(s,l,r,cmp)    sort(s+(l),s+(r)+1,cmp)
#define SORT(s,l,r)        sort(s+(l),s+(r)+1)
#define MP(x,y)            make_pair(x,y)
#define Randomize        srand( (unsigned int) time ( NULL ) )
#define INOUT(x,y)        freopen(x,"r",stdin),freopen(y,"w",stdout)

using namespace std;

typedef char name[20];

CS int MaxN = 100010 ;

struct word
{
    name x;
    int val,len;
    word()    {x[0] = 0; val = 0;}
};

struct Trie
{
    Trie * next[26];
    word * ans[10];
    Trie()
    {
        for(int i=0;i<26;i++)    next[i] = NULL ;
        for(int i=0;i<10;i++)    ans[i] = NULL ;
    }
} * Tree;

word p[MaxN];

name ask;

int n,m,asklen;

void Insert(Trie * x,int _y,int pos)
{
    int i;    word & y = p[_y];
    for(i=0;i<10;i++)
        if((x->ans[i]==NULL)||(x->ans[i]->val<y.val))    break;
    if(i<10)
    {
        for(int j=9;j>i;j--)
            x -> ans[j] = x->ans[j-1];
        x -> ans[i] = p + _y;
    }
    if(pos!=y.len)
    {
        int u = y.x[pos] - 'a';
        if(!x->next[u])    x -> next[u] = new Trie ;
        Insert(x->next[u],_y,pos+1);
    }
}

void Init()
{
    scanf("%d\n",&n);    Tree = new Trie ;
    for(int i=1;i<=n;i++)
    {
        scanf("%s %d\n",p[i].x,&p[i].val);    p[i].len=strlen(p[i].x);
        Insert(Tree,i,0);
    }
}

void Query(Trie * x,int pos)
{
    if(pos == asklen)
    {
        for(int i=0;i<10;i++)
            if(x->ans[i])    printf("%s\n",x->ans[i]->x);
            else        break;
        return ;
    }
    int u = ask[pos] - 'a';
    if(x->next[u])    Query(x->next[u],pos+1);
}

void Solve()
{
    scanf("%d\n",&m);
    while(m--)
    {
        scanf("%s\n",ask);    asklen = strlen(ask) ;
        Query(Tree,0);    if(m)    printf("\n");
    }
}

int main()
{
    Init();    Solve();
    return 0;
}

Edited by author 31.05.2012 14:40

Some hint:
For n = 4

1 : (1,2), (1,3), (1,4);
2 : (2,1), (2,3);
3 : (3,1), (3,2);
4 : (4,1);

1st have 3 friends, 2nd have 2 friends, 3d have 2 friends, 4fth have 1 friend, so ans is
4
1 2
1 3
1 4
2 3

FOR
5
-1000 10.09 21:00
+500 09.09 14:00
+1000 02.09 00:00
-1000 17.09 21:00
+500 18.09 13:00

ANSWER IS
-1000
-500
0
-500
-500

OR
-1000
-500
0
-500
0

please help me !!!!!!!!
I  submissions  14 time
this is my code
#include<stdio.h>
int main()
{   char str0[100];
    int str1[100],str2[100],str3[100];
    int i,len=0;
     gets(str0);
      for(i=0;str0[i]!='\0';i++,len++)  str1[i]=str0[i]-'a';

       str2[0]=str1[0];
       for(i=1;i<len;i++)
       {  str2[i]=str1[i];
         while(str2[i]<str2[i-1])
        {   str2[i]+=26;

         }
       }

        str3[0]=str2[0]-5;
        for(i=0;i<len;i++)
        str3[i+1]=str2[i+1]-str2[i];

       for(i=0;i<len;i++)
         printf("%c",(str3[i]%26)+'a');


}

Edited by author 28.11.2006 22:06

Edited by author 28.11.2006 22:08

What is wrong with test 4?

/// What's wrong?
var a,b,c,i,s:integer;
m:array[1..1000000] of integer;
begin
s:=0;
read(a);
read(b);
for i:=1 to b do
begin
read(m[i]);
if(m[i]>a) then
s:=s+m[i]-a
else
begin
if s>m[i]+a then
s:=s-m[i]-a
else
s:=0;
end;
end;
if s<0 then writeln(0)
else writeln(s);
end.

Sorry for my poor english.
I run code on my pc with different params. Where may be error? Test alltime is wrong. See screenshot: http://rghost.ru/59087997/image.png

Дайте тест №2, ну или все тесты на эту задачу!!!

Please don't make so stupid mistakes that I did. Lost about 3 hours on the contest, gratz to me.

Anti-WA #51:
4
0 0
2 0
1 1
1 2
Answer: oo

Anti-WA #52:
4
0 0
1 2
2 2
3 0
Answer: oo

it's very simple,especially on java.

The order of 1's within the number is 1 2 4 7 11 16 ...You can find the n'th number in sequence is equal to 1+n*(n-1)/2. So for any given input a, it is sufficient to test whether or not (a-1)*2 is equal to multiplication of two consequence number. I hope it helps

What is test case 4? please help

var n,i: integer;
x1,x2,y2,y1,xx,yy,e,r: real;
begin
 readln(n,r);
 readln(x1,y1);
 yy:=y1; xx:=x1;
 for i:=2 to n do
  begin
   readln(x2,y2);
   e:=e+sqrt(sqr(x2-x1)+sqr(y2-y1));
   x1:=x2; y1:=y2;
  end;
writeln((round((e+2*3.14159*r+sqrt(sqr(xx-x1)+sqr(yy-y1)))*100))/100);
end.

I'm using Heavy light Decomposition an I'm getting ML in test 9 WHY ????

could you give me test #7?
I can not  understand what is wrong!