#include <iostream>
#include <cassert>
#include <vector>
#include <map>
#include <set>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <math.h>
#define ll long long

using namespace std;


int main() {
    int p,d,m,s;
    cin>>p>>d>>m>>s;
    
    int curr = p;
    
    int left = s;
    
    int ans=0;
    while(1) {
        
        if (left < curr)
            break;
        left -= curr;
        curr = max(curr-d, m);
        ans++;
    }
    
    cout << ans << endl;
    
}