#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_of_game=p,number_of_games=0,flag=0;
    while(1)
    {
        if(cost_of_game>s)
        {
            break;
        }
        else
        {
            number_of_games+=1;
            if(flag==0)
            {
                s-=cost_of_game;
                cost_of_game-=d;
                if(cost_of_game<=m)
                {
                    flag=1;
                    cost_of_game=m;
                }
            }
            else
            {
                s-=cost_of_game;
            }
        }
    }
    return number_of_games;
}

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;
}