UVa 10286 Trouble with a Pentagon Solution in C / C++

Source Code

#include<stdio.h>

int main() {
  double a, b;
  while (scanf("%lf", & a) == 1) {
    b = 1.0673956817111818692592637626711 * a;
    printf("%.10lf\n", b);
  }
  return 0;
}