#include <iostream>
#include <string>
#include <bits/stdc++.h>

using namespace std;

int main(){
double n, D, H;
cin >> n >> D >> H;
vector<double> d(n), h(n);
for(int i = 0; i < n; i++) cin >> d[i] >> h[i];
  
vector<double> x(n);
double ans = 0.0;
for(int i = 0; i < n; i++){
  x[i] = H - D * (H - h[i]) / (D - d[i]);
  ans = max(ans, x[i]);
}
  
if(ans == 0) cout << "0.0" << endl;
else cout << ans << endl;
return 0;
}
 
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
#define rep(i, n) for (ll i = 0; i < (ll)(n); ++i)
#define rep2(i, s, n) for (ll i = (s); i < (ll)(n); i++)
const ll MAX = 1001001;
const ll MOD = 1000000007;
const double pi = 2.0 * asin(1.0);
ll dx[4] = {1, 0, -1, 0};
ll dy[4] = {0, 1, 0, -1};
int main()
{
    double n, d, h;
    cin >> n >> d >> h;
    vector<double> a(n), b(n);
    rep(i, n)
    {
        cin >> a[i] >> b[i];
    }
    double ans = 0;
    rep(i, n)
    {
        double k = h - d / (d - a[i]) * (h - b[i]);
        ans = max(ans, k);
    }

    cout << fixed << setprecision(10) << ans << endl;
}