51nod greatest common divisor GCD

#include <stdio.h>
long gcd(long a,long b)
{
    if(!b)
    {
        return a;
    }
    else
    {
        return gcd(b,a%b);
    }
    return 0;
}
int main(int argc,const char*argv[])
{
    long A,B;
    scanf("%ld%ld",&A,&B);
    printf("%ld\n",gcd(A,B));
    return 0;
}