#include <iostream>

using namespace std;


int main()
    {
    int p,d,m,s;
    cin >> p >> d >> m >> s;
    int k=0;
    while( s>=p )
        {
        k++;
        s -= p;
        if( p-d>=m )
            p -= d;
        else
            p = m;
        }
    cout << k;
    return 0;
    }