#include <iostream>
#include <cmath>
using namespace std;

typedef unsigned long long llg;

llg sum(llg n, llg a1, llg b) {
    return (a1*(powl(b, n)-1))/(b-1);
}

llg search(llg& n, llg& a1, llg& b, llg& max) {
    llg left = 0;
    llg right = n;
    llg middle;
    while(true) {
        middle = left+(right-left)/2;
        llg value = sum(middle, a1, b);
        if(right-left == 1) {
            if(max > value) return left;
            else return sum(left-1, a1, b);
        }
        if(value > max) {
            right = middle;
        } else if(value < max) {
            left = middle;
        } else return middle;
    }
}

int main() {
    llg n, a1, b, max;
    cin >> n >> a1 >> b >> max;
    if(n == 1 || max == a1) {
        cout << 1 << endl;
        return 0;
    }
    if(b == 1) {
        cout << (max/a1) << endl;
        return 0;
    }
    if(max < a1) {
        cout << 0 << endl;
        return 0;
    }
    cout << search(n, a1, b, max) << endl;
    return 0;
}