#include <bits/stdc++.h>
#define REP(i,a,b) for(int i=(a);i<(b);i++)
#define RREP(i,a,b) for(int i=(a);i>=(b);i--)
#define pq priotity_queue
#define P pair<int,int>
#define P2 pair<int,P>
#define P3 pair<int,P2>
typedef long long ll; typedef long double ld;
using namespace std;
const int INF=1e9, MOD=1e9+7, around[]={0,1,1,-1,-1,0,-1,1,0,0};
const ll LINF=1e18;
const ld PI=abs(acos(-1));
int n,h,a,b;

int main(){
	cin >> n >> h >> a >> b;
	a=~a+1;
	
	int mi=0,c=0,pos=h;
	while(!(pos&(1<<(n-1)))) pos+=a,mi++;
	while(!(h&(1<<(n-1)))) h+=b,c++;
	
	cout << min(mi,c) << endl;
	return 0;
}