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15 lines
173 B
15 lines
173 B
2 years ago
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#include<bits/stdc++.h>
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using namespace std;
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#define PI 3.14159265358979323
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int main() {
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int r;
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double s;
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scanf("%d",&r);
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s=PI*r*r;
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printf("%0.7lf",s);
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return 0;
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}
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