programe to find average in C

#include<stdio.h>
#include<conio.h>
void main()
{
int  a,b,c,av;
printf("enter marks of three different subject");
scanf("%d %d %d",&a,&b,&c);
av= (a+b+c)/3;

printf("\nThe average of three subject is = %d",av);
getch();
}