第一个测试点不就是样例嘛

#include <iostream>
#include <cmath>
#include <stdio.h>
using namespace std;
typedef struct mypoint {
    int x;
    int y;
}point;
long long distance(int x1, int y1, int x2, int y2) {
    return (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
}
int main()
{
    int N;
    cin >> N;
    point poi[1005];
    for (int i = 0; i < N; i++) {
        cin >> poi[i].x >> poi[i].y;
    }
    long long max = 0;
    long long temp;
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++) {
            long long dis = distance(poi[i].x, poi[i].y, poi[j].x, poi[j].y);
            if (max < dis) {
                max = dis;
            }
        }
        if (i == 0) {
            temp = max;
        }
        if (temp > max)
            temp = max;
    }
    printf("%.4f", (double)temp * 3.1415926535);
}