#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <string>
#include <iomanip>
#include <functional>
#include <deque>
#include <stack>
#include <queue>
#include <bitset>
#include <map>
#include <set>
#include <unordered_set>
using namespace std;
typedef long long ll;
#define rep(i,n) for (ll i = 0; i < (ll)(n); i++)
#define REP(i,n) for (ll i = 1; i <= (ll)(n); i++)
#define all(v) v.begin(), v.end()
#define pb push_back
#define fcout cout<<fixed<<setprecision(15)
#define PI 3.1415926535897932384626433832795028841971693993751058209749445923078160628620899
const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const ll INF = 1000000000000000000;
const ll NIL = -1;
const ll dx[4] = { 0,1,0,-1 };
const ll dy[4] = { 1,0,-1,0 };

double N, D, H, d[1010], h[1010];

int main() {
	cin >> N >> D >> H;
	rep(i, N) cin >> d[i] >> h[i];
	double ans = 0;
	rep(i, N) {
		double k;
		k = (H - h[i]) * D / (D - d[i]);
		ans = max(ans, H - k);
	}
	fcout << ans << endl;
	return 0;
}
#include <iostream>

using namespace std;

int main(){
	ios::sync_with_stdio(false);
  	cin.tie(0);
  	int a,b,c,d;
  	cin>>a>>b>>c>>d;
  	cout<<a*d-c*b<<'\n';
}