How to find greatest of 3 numbers using function using return?

CODE

How to find greatest of 3 numbers using function using return?

//Write a program to find greatest of 3 numbers using function using return…..

int main()

{

    int a,b,c,max;

    printf("\n enter a,b,c:");

    scanf("%d%d%d",&a,&b,&c);

    int gr(int a,int b,int c);

    max=gr(a,b,c);

    printf("\n greatest value=%d",max);

}

int gr(a,b,c)

{

    if(a>b)

    {

        if(a>c)

            return a;

        else

            return c;

    }

    else

        if(b>c)

            return b;

        else

            return c;

}

Output:

enter a,b,c:

45

78

12

 greatest value=78