#include <iostream>
#include <cmath>
using namespace std;
//formula is n =  and log(q)!=0 and b (q - 1) q (b + m (q - 1))!=0 and c_1 element Z
int main() {
    int a1, b;
    unsigned long long n, MAX;
    scanf("%llu%d%d%llu", &n, &a1, &b, &MAX);
    unsigned long long cur = a1;
    unsigned long long curam = a1;
    unsigned long long plates = n;
    double fplates = 0;
    if (a1 > MAX) {
        printf("0\n");
        return 0;
    }
    if (b == 1) {
        plates = floor(MAX / a1);
        if (plates > n) plates = n;
    }else {
        fplates = (log((MAX * (b - 1)) / a1 + 1)) / log(b);
        fplates = floor(fplates);
        if (fplates > n) fplates = n;
        plates = fplates;
    }


    printf("%llu", plates);
}