辗转相除

  #include<bits/stdc++.h>
  using namespace std;

  int main(){

  int a, b;
  scanf("%d%d",&a, &b);
  int k = 0;
  while(k = a % b)
  {
      a = b;
      b = k; 
   }
   printf("%d",b);

  return 0;
}