#include<bits/stdc++.h>
using namespace std;
int main()
{
    ios::sync_with_stdio(0);cin.tie(0);

    int n;cin>>n;
    double x,y;cin>>x>>y;
	
    double ans=1e18;
    for(int i=1;i<=n;i++)
	{
        double a,c;cin>>a>>c;
        double b=-1;
        double d=fabs((a*x+b*y+c)/sqrt(a*a+b*b));
        ans=min(ans,d);
    }
    cout<<fixed<<setprecision(2)<<ans;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
    ios::sync_with_stdio(0);cin.tie(0);

    int n;cin>>n;
    double x,y;cin>>x>>y;
	
    double ans=1e18;
    for(int i=1;i<=n;i++)
	{
        double a,c;cin>>a>>c;
        double b=-1;
        double d=fabs((a*x+b*y+c)/sqrt(a*a+b*b));
        ans=min(ans,d);
    }
    cout<<fixed<<setprecision(2)<<ans;
    return 0;
}