51nod 最大公约数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;}