#include <bits/stdc++.h>

using namespace std;

int main() {
    int p;
    int d;
    int m;
    int s;
    cin >> p >> d >> m >> s;
    int count = 1;
    long long sum = p;
    int a = p;
    
    if(s < p)
        cout<<"0";
    else
    {
    while(true)
    {
            a = a - d;
        if (a <= m)
            a = m;
        
        sum = sum + a;
        if(sum <= s)
            count = count + 1;
        else
            break;
    }
    
    cout<<count;
    }
}