求两个数的最小公倍数和最大公约数C++

#include<iostream>
using namespace std;
//求两个数的最大公约数
int max_common_divisor(int a,int b)
{
    int t;
    if(a<b)
    {
     t=a;a=b;b=t;
    }
    t=a%b;
    while(t!=0)
    {
        a=b;b=t;t=a%b;
    }
    return b;
}
int main()
{
    int m,n,c,Big;
    cout<<"Input m,n:";
    int flag=1;
    while(flag)
    {
       cin>>m>>n;
       c=m*n;
       if(c==0)
           cout<<m<<"and"<<n<<"has no common divisor.Please input again!\n";
       else if(c<0||(m<0&&n<0))
          cout<<"this is not what we want!Please input again!\n";