#include
using namespace std;
void Scholarship(int n,int m,int x,int y)
{
int l=0;
int h=n;
int mid=0;
int Max=0;
int a=0;
int b=0;
while(l<=h)
{
mid=(l+h)/2;
a=mid*x;
b=(m+(n-mid)*y);
if(a<=b)
{
Max=mid;
l=mid+1;
}
else
h=mid-1;
}
cout<<Max;
}
int main()
{
int n,m,x,y;
cin>>n>>m>>x>>y;
Scholarship(n,m,x,y);
}