#include <cstdio>
#include <vector>
using namespace std;

int main() {
    int p, d, m, s;
    if (4 != scanf("%d %d %d %d", &p, &d, &m, &s)) { return 1; }
    int count=0;
    for (int cost=p; s >= cost; ++count) {
        s -= cost;
        cost = (cost-d > m ? cost-d : m);
    }
    printf("%d\n", count);

    return 0;
}