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