#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
    long int sum,b;
    int c,a,t;
    for(a=p,sum=0,c=0;sum<=s;c++)
    {//printf("%ld ",sum);
        sum=sum+a;
        t=a-d;
        if(t<m) 
           a=m;
        else a=t;
    }
    return c-1;
}

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;
}