注意 $pi$ 的取值为 $3.1415926535$

(huhe说的)

是temege P2832 弗雷德的困惑吧

#include <iostream>
#include <stack>
#include <cmath>
#include <vector>
#include <string.h>
#include <queue>
#include <stdio.h>
#include <iomanip>
#include <cstdio>
#include <algorithm>
#define int long long
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f;
const long double P = 3.1415926535;
using namespace std;
signed main()
{
    int x, y, day;
    cin >> x >> y;
    day = ((x * x + y * y) * M_PI / 100);
    cout << day;
    return 0;
}