Problem A. Area and Circumference

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define fastio ios::sync_with_stdio(false),cin.tie(0);
#define pll pair<ll,ll>
#define F first
#define S second
#define pb push_back
#define ppb pop_back()
#define mkp make_pair
#define sz(a) (ll)a.size()
#define all(x) x.begin(),x.end()

const ll MAXN=2e5+5;
const ll INF=1e18;
const ll MOD=998244353;

ll N;

void init(){
    cin>>N;
    ll a,b,c,d;
    double ans=0;
    while(N--){
        cin>>a>>b>>c>>d;
        double h=c-a;
        double w=b-d;
        double tmp=(h*w)/double(2*(h+w));
        ans=max(ans,tmp);
    }
    printf("%1f\n",ans);
}

void solve(){

}

signed main(){
    fastio
    freopen("area.in","r",stdin);
    freopen("area.out","w",stdout);
    // ll T;
    // cin>>T;
    // while(T--){
        init();
        solve();
    // }
    return 0;
}