I don't understand why WA#4 here is my code(maybe I use uncorrect algo?):
#include<iostream>
#include<cmath>
#include<stdio.h>
using namespace std;
int main()
{
    unsigned __int64 k=0;
    long r;
    cin>>r;
    if(r==1)
    {
        cout<<4<<endl;
        return 0;
    }
    if(r==2)
    {
        cout<<16<<endl;
        return 0;
    }
    k=(r-1)*8;
    k=k+(r-1+r-1)*(r-1+r-1);
    printf("%I64u\n",k);
    return 0;
}

Wrong algo :]
For example:
r = 5
correct_answer  = 88

Your formula:
a = 8*(5-1) = 8*4 = 32
b = (r-1+r-1)*(r-1+r-1) = (2r-2)^2 = 8^2 = 64
res = a+b = 32 + 64 = 96

correct_answer != res -> Wrong algo :]

Edited by author 12.06.2009 01:14