#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <numeric>
#include <array>
#include <set>
#include <map>
#include <queue>
using namespace std;
 
#define REP(i,n) for(int (i)=0;(i)<(int)(n);(i)++)
#define RREP(i,n) for(int (i)=(int)(n)-1;i>=0;i--)
#define REMOVE(Itr,n) (Itr).erase(remove((Itr).begin(),(Itr).end(),n),(Itr).end())
typedef long long ll;

ll N,X,A,B;

bool check1(long long x) {
    ll t = X - x * A;
    if (t <= 0) return true;
   return false;
}

long long BinarySearchMin1(long long low, long long high) {
    while (high - low > 1){
        long long mid = (low + high) / 2;
        if (check1(mid)) high = mid;
        else low = mid;
    }
    return high;
}

bool check2(long long x) {
    ll t = X + x * B;
    if (t >= (1LL << (N - 1))) return true;
   return false;
}

long long BinarySearchMin2(long long low, long long high) {
    while (high - low > 1){
        long long mid = (low + high) / 2;
        if (check2(mid)) high = mid;
        else low = mid;
    }
    return high;
}

int main() {

    cin >> N >> X >> A >> B;

    cout << min(BinarySearchMin1(0, 1LL << 31LL), BinarySearchMin2(0, 1LL << 31LL)) << endl;

    return 0;
}