Submission #1521505

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Source Code Expand

#include <bits/stdc++.h>
//#define _USE_MATH_DEFINES
//#include <cmath>

using namespace std;

typedef pair<int, int> P;

int n;
priority_queue<int> q;
long double ans;
int tmp;

const long double PI = 3.14159265;

int main() {
  while (cin >> n && n) {
    ans = 0;
    for (int i = 0; i < n; i++) {
      cin >> tmp;
      q.push(tmp);
    }
    while (!q.empty()) {
      if (q.size() == 1) {
        int p = q.top(); q.pop();
        ans += p*p*PI;
        continue;
      }
      int b = q.top(); q.pop();
      int s = q.top(); q.pop();
      ans += b*b*PI - s*s*PI;
    }
    cout << fixed << setprecision(6) << ans << endl;
    while (!q.empty()) q.pop();
  }
  return 0;
}

Submission Info

Judge Result