Submission #3435144

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Source Code Expand

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

int main() {
  int N;
  cin >> N;
  vector<int> r(N);
  for(int i=0;i<N;i++){
    cin >> r.at(i);
  }
  sort(r.begin(),r.end());
  reverse(r.begin(),r.end());
  double ans=0.0;
  int fugou =1;
  for(int i=0;i<N;i++){
    ans = ans +fugou*r.at(i)*r.at(i);
    fugou *=-1;
  }
  ans *= 3.141592653589793;
  cout << ans << endl;
}
  

Submission Info

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