#include <iostream>
#include <algorithm>
#include <cmath>

using namespace std;

int main()
{
    long long int n;
    double a, b, maximum,r;
    cin >> n >> a >> b >> maximum;
    if (b == 1)
    {
        long long int r1 = (long long int)(maximum/a);
        cout << min(n, r1);
        return 0;
    }
    r = (log(((maximum*(b-1))/a)+1))/(log(b));
    long long int r2 = ((long long int)r);
    cout << min(n, r2);
}