5.17

#include<iostream>

using namespace std;

int main()

{

       int x,y;

       cin>>x>>y;

       if (x < y)

       {

              int tmp = y;

              y = x;

              x = tmp;

       }

       for (int i = y; i >= 1; i-- )

       {

              if (x%i == 0 && y%i == 0)

              {

                     return i;

              }

       }