#include<bits/stdc++.h>
using namespace std;
int main(){
	double a,b;
	cin>>a>>b;
	cout<<(1-b/a)*100; 
	return 0;	
}
#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define all(a) a.begin(),a.end()
using namespace std;
using ll=long long;
using P=pair<int,int>;
template<typename T>
using v=vector<T>;
template<typename T>
using vv=vector<v<T>>;
template<typename T>
using vvv=vector<vv<T>>;

int main(){
    int n;
    double D,H;
    cin>>n>>D>>H;
    double ret=0;
    rep(i,n){
        double d,h;
        cin>>d>>h;
        ret=max(ret,h-(H-h)*d/(D-d));
    }
    cout<<setprecision(16)<<ret<<endl;
}
