#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 k,l,t=0;
    k=p;
    l=k;
    while(k<=s){
        if(l-d>=m){
            l=l-d;
        }
        else 
            l=m;
        
        k=k+l;
       
        t++;
    }
    if(k<=s)
        t=t-1;
    return t;
}

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;
}