#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 diff = p - m;
    int last;
    if (diff % d == 0){
        last = m + d;
    }else{
        last = p - d*(diff/d);
    }
    
    int terms = (p - last)/d + 1;
    int sum = terms*(last + p)/2;
    
    if(sum <= s){
        int rem = s - sum;
        return terms + rem/m;
    }//*/
    
    int ct = 0;
    int rem = s;
    int gp = p;
    while(rem > gp && gp > m){
        rem -= gp;
        ct++;
        gp -= d;
    }
    
    return ct;
    
    //printf("%d %d\n", ct, rem);
    
    //return ct + (rem/m);
    
    /*
    while(rem > gp){
        
    }
    
    return ct;//*/
}

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;
}