#include <stdio.h>
int main(void) {
// your code goes here
const double PI=3.14159;
double r;
printf("zhouchang=%f\n",2*PI
*r
); return 0;
}
I2luY2x1ZGUgPHN0ZGlvLmg+CgppbnQgbWFpbih2b2lkKSB7CgkvLyB5b3VyIGNvZGUgZ29lcyBoZXJlCiAgICBjb25zdCBkb3VibGUgUEk9My4xNDE1OTsKICAgIGRvdWJsZSByOwogICAgc2NhbmYoIiVsZiIsJnIpOwogICAgcHJpbnRmKCJ6aG91Y2hhbmc9JWZcbiIsMipQSSpyKTsKICAgIHByaW50ZigibWlhbmppPSVmXG4iLFBJKnIqcik7CglyZXR1cm4gMDsKfQo=