#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 sum = 0 ;
    int count = 0;
    int i ;
    for(i = p ; i > m && sum <= s; i = i-d )
    {
        sum += i;
        ++count;
    }
    while(sum <= s)
    {
        sum += m;
        ++count;
    }
    return count-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;
}