#include<bits/stdc++.h>
using namespace std;
int main(){
long long int n,m,x,y;
cin>>n>>m>>x>>y;
int s=0,e=n,ans;
while(s<=e){
long long int mid=(s+e)/2;
long long int z=(mid*x);
long long int d=m+((n-mid)*y);
if(z<=d){
ans=mid;
s=mid+1;
}
else{
e=mid-1;
}
}
cout<<ans<<endl;
}