#include <iostream>
#include <cstdio>

using namespace std;

typedef long long ll;
typedef double flt;

const char eol = '\n';

int main()
{
  /*
    freopen("tmp", "r", stdin);
//  */ ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    
    int m, p, d, s;
    cin >> p >> d >> m >> s;
    
    int cur_cost = p, res = 0;
    while (cur_cost <= s)
    {
        ++res;
        s -= cur_cost;
        
        cur_cost = max(cur_cost - d, m);
    }
    
    cout << res << eol;
    
    return 0;
}