#include <iostream>
using namespace std;
long long powl(int a, int n) {
	if (n <= 1) return 1;
	if (n % 2 == 1) return powl (a, n-1) * a;
	else {
		int b = powl (a, n/2);
		return b * b;
	}
}
long long log( long long n, long long a){
   if(n == 1) return 1;
   return 1 + log(n/a, a);
}
long long geoma(long long cnt, long long a , long long b){
	return (a * (powl(b,cnt) - 1) / (b - 1));
}
int main(){
  freopen("in.txt","r",stdin);
	long long  n ,a ,b,mx;
	cin >> n >> a >> b >> mx;
	if (b == 1){
		cout << min(mx/a , n);
	 	return 0;
	}
	long long  ans = 0;


	// cnt  =
	long long cnt = log(9 * mx + (a/(b-1)), b);
	if (cnt > n ){
		cnt = n;
	}
	while(cnt){
		if (geoma(cnt , a , b) <= mx){
			cout << cnt;
			return 0;
		}
		cnt --;
	}
}