c_1

#include <iostream>
using namespace std;
int main() {
	int a1, b, max = 0, n, k = 0;
	cin >> n >> a1 >> b >> max;
	while (n != 0 && (max - a1) >= 0) {
		max -= a1;
		a1 = a1 * b;
		n--;
		k++;
	}
	cout << k;
	return 0;
}