#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>

int howManyGames(int p, int d, int m, int s) {
    // Return the number of games you can buy
    int ans = 0;
    while(s > p && p > m) {
        s -= p;
        //printf("(%d)",p);
        ans++;
        if(p-d <= m) p = m; else p -= d;
    }
    if(p == m) ans += (int)floor((double)s/(double)m);
    return ans;
}

int main() {
    int p; 
    int d; 
    int m; 
    int s; 
    scanf("%i %i %i %i", &p, &d, &m, &s);
    int answer = howManyGames(p, d, m, s);
    printf("%d\n", answer);
    return 0;
}