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

int max(int a, int b){
    return(a>b)?a:b;
}

int howManyGames(int p, int d, int m, int s) {
    // Return the number of games you can buy
    int p_c = p,num_games_bought = 0;
    while(s >= p_c){
        s -= p_c;
        p_c = max(p_c - d, m);
        num_games_bought++;
    }
    return num_games_bought;
}

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;
}