#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 number_of_games = 0;
    int total_cost = 0;
    int current_cost = p;
    while(1)
    {
        total_cost+=current_cost;
        if(total_cost > s)
            break;
        number_of_games++;
        if(current_cost > m)
        {
            current_cost-=d;
            if(current_cost < m)
            {
                current_cost = m;
            }
        }
        else
            current_cost = m;
        //printf("%d ", current_cost);
    }
    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;
}