#include <iostream>
using namespace std;

int main()
{
    long double u,v,r;
    int n,k;
    cin >> n >> k >> u >> v;
    r=(((k-1)*v)+15)/u;
    if(k==1)r=(k*v)/u;
    if(r+5>n)cout << 1 << endl;
    else cout << n-(int)r << endl;

    return 0;
}

Edited by author 02.06.2008 22:16

Edited by author 02.06.2008 22:17

Oh! I think that you are not right at r. Because the elevator goes down and then waits for 15 minute, after that it goes up. So your fomular computes r is wrong! ^_^.

Edited by author 07.11.2008 05:38