#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <climits>
#include <map>
using namespace std;

int main()
{
    int tests;
    int i, j, k, len;
    int a, p;
    int total_sum = 0;

    scanf("%d %d %d %d", &i, &j, &k, &len);
    tests = i;
    p = 0;
    while (total_sum <= len)
    {
        total_sum += tests;
        tests -= j;
        if (tests < k)
        {
            tests = k;
        }
        if (total_sum <= len)
        {
            p++;
        }
    }

    printf("%d\n", p);

    return 0;
}