distanceofpairs.cpp

#include<iostream>
#include<vector>

#pragma GCC optimize("03")
#pragma GCC target("avx2")

#define long long long
#define nln '\n'

using namespace std;

long sqr(long x)
{
    return x*x;
}

long distance(pair<long, long> a, pair<long, long> b)
{
    return sqr(b.first-a.first) + sqr(b.second-a.second);
}

int main()
{
    cin.tie(0)->sync_with_stdio(0);
    cout.tie(0)->sync_with_stdio(0);
    // Input
    //freopen("distanceofpairs.inp", "r", stdin);
    long n;
    cin >> n;
    vector<pair<long, long>> a(n);
    for (auto &i : a)
        cin >> i.first >> i.second;
    // Process
    long ans = 0;
    for (long i = 0; i < n-1; ++i)
        for (long j = i+1; j < n; ++j)
            ans += distance(a[i], a[j]);
    // Output
    cout << ans << nln;
    return 0;
}