#include <stdio.h>
#include <math.h>

using namespace std;

int main() {
    
    double p, q, r;
    
    scanf("%lf%lf%lf", &p,&q,&r);
    
    double a, b, s;
    
    a = (p+q)*(p+q)*2;
        
    b = p*p*2;
    
    s = sqrt(a * b);
    
    printf("%.4lf\n", s);
    
    return 0;
}
