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OI-codes/AcWing/604/604.cpp

13 lines
201 B
C++

#include <bits/stdc++.h>
using namespace std;
const double pi = 3.14159;
int main() {
double r;
cin >> r;
cout << "A=" << fixed << setprecision(4) << pi * r * r << endl;
return 0;
}