#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 cost=p,total=0,update=0;
    int count=-1;
   do
   {
       count++;
       if(cost==0){
        total=total+p;
       }
       else
       {
           if((cost-d)>m){
           cost=cost-d;
               total=total+cost;
           }
           else{
               cost=m;
           total=total+cost;
           }
       }
      
   }while(total<s);
       return count-2;
}

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;
}