euclidean algorithm for gcd.cpp

In number theory, the Euclidean algorithm (also called Euclid s algorithm) is an algorithm to determ

// 436.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream.h>
int mod(int u,int v)
{
	int t,r;
	if(u>v && v==0)
		return u;
	if(u<v && u==0)
		return v;
	else 
		if(v>u && u!=0)
	{
		t=u,u=v,v=t;
	}
	while((r=u%v)!=0)
	{
		u=v;
		v=r;
	}
	return (v);
}


int gcd(int m,int n)
{   
	int mod(int x,int y);
	int l;
    l=mod(m,n);
	return l;
	
}

int main()
{
	int a,b,c;
	cin>>a>>b;
	if(a<0 || b<0)
	{	
		cout<<"data error!";
	}
	else
		if(a==0 && b==0)
		{
			cout<<"data error!";
		}
			c=gcd(a,b);
			cout<<c<<endl;
			return 0;
}