#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 i,j,sum=0,cnt=0;
    i=p;
    while(i>=m)
    {
        sum=sum+i;
        i=i-d;
        if(sum>s)
            break;
        else
            cnt++;
    }
    
    while(true)
    {
        if((sum+m)<=s)
        {
            sum=sum+m;
            cnt++;
        }
        else
            break;
     }
    return cnt;
    
}

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;
}