#include <iostream>
#include <string>

int n = 0, a = 0, b = 0, max = 0;
int prevA = 0;
int A = 0;
int i = 1;
int val = 0;
int main()
{      std::cin >> n >> a >> b >> max;
A = a;
val = val + A;
//  std::cout << "A:  "  << A << std::endl;
    while (A <= max && val <= max){
    	A = A*b;
    	val = val + A;

   //std::cout << "A:  "  << A << "    " << "val:   " << val <<std::endl;

		if (val <= max){
			if ( i < n){
					i = i + 1;
			}

		}

	}
std::cout << i ;
        return 0;
}