Submission #1695728

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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(), greater<int>());

    int sum = 0;
    for (int i = 0; i < n; i++) {
        int r2 = v[i] * v[i];
        sum += (i & 1) ? -r2 : r2;
    }

    printf("%.15f\n", sum * M_PI);

    return 0;
}

Submission Info

Judge Result