Submission #1695713

---

Source Code Expand

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

#define DEBUG(x) cerr << #x << ": " << x << endl;
#define ll long long

int main() {
    int n; cin >> n;

    vector<int> v(n);
    for (int i = 0; i < n; i++) {
        cin >> v[i];
    }
    sort(v.begin(), v.end());

    double sum = 0;
    for (int i = 0; i < n; i++) {
        int r = v[i];
        if (i % 2 == 0) sum += M_PI * r * r;
        if (i % 2 != 0) sum -= M_PI * r * r;
    }

    cout << abs(sum) << endl;

    return 0;
}

Submission Info

Judge Result