#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    // Return the number of games you can buy
    int sum = p;
    s = s-p;
    int x = p;
    int count = 1;
    while(s >= 0){
        if(x-d > m)
            x = x-d;
        else
            x = m;
        sum += x;
        s -= x;
        count++;
    }
    return count-1;
}

int main() {
    int p;
    int d;
    int m;
    int s;
    cin >> p >> d >> m >> s;
    int answer = howManyGames(p, d, m, s);
    cout << answer << endl;
    return 0;
}