#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)
{
   int sum=0,count=0,price=p;
   while(1)
   {
       sum+=price;
       if(sum>s)break;
       count++;
       if((price-d)>m)
           price-=d;
       else  price=m;       
   }
    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;
}