C :

int main(int argc, char* argv[])
{
	int a,b,c;
	while(~scanf("%d%d%d",&a,&b,&c))
	{
	  printf("%.2lf\n",(a+b+c)/3.0);
	}
	return 0;
}

C++ :

#include <iostream>
#include<iomanip>
using namespace std;

int main()
{
    int a,b,c;
    int sum;
    double average;
    cin>>a>>b>>c;
    sum=a+b+c;
    average=sum*1.0/3;
    cout<<fixed<<setprecision(2);
    cout<<average<<endl;
    return 0;
}

Pascal :

program aa;
var
  a,b,c,d:real;
begin
  readln(a,b,c);
  d:=(a+b+c)/3;
  writeln(d:0:2);
end.