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