#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) {
    if(p>s)
        return 0;
    if(p==s)
        return 1;
    int count = 0;
    int sum = 0,tempP = p;
    while(tempP>m && sum<s){
        sum+=tempP;
        tempP-=d;
        count++;
    }
    while(sum<s){
        sum+=tempP;
        if(sum<=s)
            count++;
    }
    return count;
}

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-1);
    return 0;
}