#include <iostream>
#include <cmath>

int main() {
    using namespace std;
    long long n, x, a, b;
    cin >> n >> x >> a >> b;
    long long nmax;
    nmax = (long long)pow(2., n-1) - 1;
    long long atime = x % a ? x / a + 1 : x / a;
    long long nover = nmax - x + 1;
    long long btime = nover % b ? nover / b + 1 : nover / b;
    long long ntime = atime < btime ? atime : btime;
    cout << ntime << endl;
}