codeforces 732A Buy a Shovel（水题）

#include<bits/stdc++.h>
using namespace std;
int main()
{int k,r;cin>>k>>r;for(int i=1;;i++){if((k*i)%10==0){printf("%d\n",i);break;}else if((k*i-r)%10==0){printf("%d\n",i);break;}}return 0;
}