#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) {
    int currs = s, out = 0, currp = p;
    
    while(currs > 0) {
        currs -= currp;
        out++;
        currp -= d;
        if(currp < m) {
            currp = m;
        }
    }
    
    if(currs < 0) {
        out--;
    }
    
    return (out);
}

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;
}