#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    
    int p, d, m, s;
    
    std::cin >> p;
    std::cin >> d;
    std::cin >> m;
    std::cin >> s;
    
    int c = 0;
    
    while (p <= s) {
        s -= p;
        c++;
        
        if (p > m) {
            p -= d;
        }
        if (p < m) {
            p = m;
        }
    }
    
    std::cout << c;
    
    
    return 0;
}