Bài toán tính ước chung lớn nhất bằng C++

Cho một số m, n tìm ước chung lớn nhất của chúng. Ta có code như sau:

#include <iostream.h>
void main(){
                     int m,n,kq;

                     cout<<"Moi nhap vao m,n: ";
                     cin>> m >> n;

                     if(m>n){
                                   for(i=0;i<=n;i++){
                                                                if(n%i==0 && m%i==0)
                                                                         i=kq;
                                                                }
                     }
                     else{
                                   for(i=0;i<=m;i++){
                                                                if(m%i==0 && n%i==0)
                                                                         i=kq;       
                                                                 }
                    }

                    cout<<"UCLN: "<<kq;

                    getch();
}