Templates practice (Averege Of three arrays)

#include<iostream>
using namespace std;
template<class T>
T calc(T a[],int size)
{
 T sum=0,res=0;
 for(int i=0;i<size;i++)
 {
  sum=sum+a[i];
 }
 res=(sum/size);
 return res;
}

void main()
{
 int a[]={2,7,6,8,7,8};
 cout<<"The average is "<<calc(a,6)<<endl;
 float b[]={2.09,7.14,8.7,7.9,8.2};
 cout<<"The average is "<<calc(b,5)<<endl;
 long c[]={200, 600, 8010, 950, 7890, 6788};
 cout<<"The average is "<<calc(c,6)<<endl;

}