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

int howManyGames(int first, int diff, int atleast, int budget) {
    int result = 0;
    while(1) {
        budget -= first;
        if(budget < 0) {
            return result;
        }
        
        result++;
        if(first - diff >= atleast) {
            first -= diff;
        } else {
            first = atleast;
        }
        
    }
    return result;
}

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;
}