#include
using namespace std;
bool poss(int n,int dhas,int r,int g,int p){
if((p*r)<=dhas+((n-p)*g)){
return true;
}
return false;
}
int main() {
int n,m,x,y;
cin>>n>>m>>x>>y;
int s=0;
int e=n;
int ans=0;
while(s<=e){
int mid=(s+e)/2;
if(poss(n,m,x,y,mid)){
ans=mid;
s=mid+1;
}
else{
e=mid-1;
}
}
cout<<ans<<endl;
return 0;
}