#include <stdio.h>
#include <math.h>
int main() {
double a, b, c, R;
printf("a=");
scanf("%lf", &a);
printf("b=");
scanf("%lf", &b);
printf("c=");
scanf("%lf", &c);
R = (c * sqrt(a * b + c * c)) / sqrt((2 * c - a + b) * (2 * c + a - b));
printf("%.3f", R);
return 0;
}
