#include<bits/stdc++.h>
using namespace std;
//#define int long long
#define REP(i,m,n) for(int i=(m);i<(n);i++)
#define rep(i,n) REP(i,0,n)
#define pb push_back
#define all(a) a.begin(),a.end()
#define rall(c) (c).rbegin(),(c).rend()
#define mp make_pair
#define endl '\n'
#define vec vector<ll>
#define mat vector<vector<ll> >
#define fi first
#define se second
#define double long double
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll,ll> pll;
//typedef long double ld;
typedef complex<double> Complex;
const ll INF=1e9+7;
const ll MOD=INF;
const ll inf=INF*INF;
const ll mod=MOD;
const ll MAX=100010;



signed main(){
    ll n;cin>>n;
    double d,h;cin>>d>>h;
    double ans=0;
    rep(i,n){
        double a,b;cin>>a>>b;
        ans=max(ans,h-(h-b)*d/(d-a));
    }
    cout<<fixed<<setprecision(10)<<ans<<endl;
}
#include <bits/stdc++.h>
using namespace std;

#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define rep3(i,m,n) for(int (i)=m;(i)<=(n);(i)++)
#define rep3rev(i,m,n) for(int (i)=m;(i)>=(n);(i)--)
#define all(a) (a.begin()),(a.end())
#define rall(a) (a.rbegin()),(a.rend())
#define fi first
#define se second
#define pb push_back
#define eb emplace_back

using ll = long long;
using vll = vector<ll>;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using P = pair<int, int>;
using LD = long double;

template <typename T> bool chmax(T &a, const T &b) { if (a < b) { a = b; return true; } return false; }
template <typename T> bool chmin(T &a, const T &b) { if (a > b) { a = b; return true; } return false; }
void yes(bool ok = true){ cout << (ok ? "yes" : "no") << endl; }
void Yes(bool ok = true){ cout << (ok ? "Yes" : "No") << endl; }
void YES(bool ok = true){ cout << (ok ? "YES" : "NO") << endl; }

LD memo[105][105][105];

LD dfs(int a, int b, int c){
    if(memo[a][b][c] != 0) return memo[a][b][c];
    if(a == 100 || b == 100 || c == 100) return memo[a][b][c] = 0;
    LD sum = a + b + c;
    return memo[a][b][c] = a * (dfs(a+1, b, c)+1) / sum + b * (dfs(a, b+1, c)+1) / sum + c * (dfs(a, b, c+1)+1) / sum;
}

void Main(){
    int a, b, c; cin >> a >> b >> c;
    cout << dfs(a, b, c) << endl;
    return;
}

int main(){
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(15);
    Main();
    return 0;
}