#include <iostream>
#include <math.h>
using namespace std;
double stud(double arg1, double arg2);
int main()
{
  double a,b,c;
cin >> a;
cin >> b;
c = stud(a, b);
cout << c*c;
}
double stud(double arg1, double arg2)
{return (arg1+arg2)/2;}



int main()
{int a,b;
    bool c=true;
cout<<"vvedite chislo";
  cin>>a;
  for (b=2;b<sqrt (double(a));b++)
  {
   if (a%b==0)
      c=false;

}
  if(c)
      cout<< "Yes";
  else
      cout<<"No";
}