#include <bits/stdc++.h>   using namespace std;   long long k, b, n, t, ans, cur;   int main() {     ios_base::sync_with_stdio(0);     cin >> k >> b >> n >> t;     ans = n;     cur = k + b;     while (cur <= t) {       cur = cur * k + b;       --ans;     }     if (ans < 0) ans = 0;     cout << ans << endl;     cin.get();     cin.get();     return 0;   }   