#include<iostream> #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ double r,p=3.1415926; scanf("%lf",&r); printf("%.2lf",p*r*r return 0; }