#include<bits/stdc++.h>
using namespace std;
int main(){
    double a,b,c;
    cin>>a>>b>>c; 
    if(a+b>c&&a+c>b&&b+c>a){
        double s=(a+b+c)/2.0;
        double n=sqrt(s*(s-a)*(s-b)*(s-c));
        printf("%.2f\n", n);
    }
    else
        cout<<"No solution."<<endl;
    return 0;
}