Greatest Comman Devider ( GCD ) of two numbers

/*find gratest common devider of given two nombers*/

#include<stdio.h>

//Function to find GCD from Euclid's algorithm:


long int gcd(long int a, long int b)
{
    if (b > a)
    {

        return gcd(b, a);
    }
    if (b == 0)
    {

        return a;
    }
    else
    {
        return gcd(b, a % b);
    }
}

void main()
{
    long int a, b;
    long int gcd(long int, long int);

    //   clrscr();
    printf("Program to finf greatest comman devider: ");
    printf("\nEnter first number: ");
    scanf("%ld", &a);

    printf("\nEnter second number: ");
    scanf("%ld", &b);
    printf("\nGreatest comman devider is: %ld", gcd(a, b));

    //    getch();
}