Longest Segment

#include <bits/stdc++.h>
using namespace std;

#define F first
#define S second
#define int long long
#define double long double

int distance(int x1 , int y1 , int x2, int y2){
    int d = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
    return d;
}

signed main()
{
    int n;
    cin >> n;
    vector<pair<int , int> > v(n);
    for(int i = 0; i < n; i++){
        cin >> v[i].F >> v[i].S;
    }
    int ans = 0;
    for(int i = 0; i < n; i++){
        for(int j = i + 1; j < n; j++){
            ans = max(ans , distance(v[i].F , v[i].S , v[j].F , v[j].S));
        }
    }
    double sq = sqrtl(ans);
    cout << setprecision(6) << fixed << sq << endl;
}