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模板题，泰裤辣（洛谷真奇妙）

#include<bits/stdc++.h>
using namespace std;
const int maxn = 5e5 + 5;
struct node{
    int x,y,lx,ly;
}p[maxn];
bool cmp(node A,node B){
    if(A.x < B.x || (A.x == B.x && A.y < B.y)) return 1;
    else return 0;
}
int dis(node A,node B){return (A.lx - B.lx) * (A.lx - B.lx) + (A.ly - B.ly) * (A.ly - B.ly);}
int main(){
    int n; cin >> n;
    for(int i = 1;i <= n;i++){
        int X,Y;
        cin >> X >> Y;
        p[i].lx = X;
        p[i].ly = Y;
        p[i].x = X * cos(1.14) - Y * sin(1.14);
        p[i].y = X * sin(1.14) + Y * cos(1.14);
    }
    sort(p + 1,p + n + 1,cmp);
    int ans = 0;
    for(int i = 1;i <= min(20000,n);i++){
        for(int j = n - min(20000,n) + 1;j <= n;j++) ans = max(ans,dis(p[i],p[j]));
    }
    cout << ans;
    exit(0);
}