#include <bits/stdc++.h>

using namespace std;

long long int howManyGames(long long int p,long long int d,long long int m,long long  int s) {
    // Return the number of games you can buy
    long long int count = 0 , h = 0;
    while(h < s)
    {
        if(h + p > s)
        {
            break;
        }
        h = h + p;
        if(p > m)
        p = p - d;
        if(p < m)
        {
            p = m;
        }
        
            count++;
    }
    return count;
}

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