//#include #include<stdio.h> #include<math.h> using namespace std;

int main() { int a,b,c,p; double s; scanf("%d%d%d",&a,&b,&c); //cin>>a>>b>>c; p=(a+b+c)/2; s=sqrt(p*(p-a)(p-b)(p-c)); //cout<<s<<endl; printf("%.1lf",s);

return 0;

}