RT,本人蒟蒻大佬踩爆我，附上代码

#include<iostream>
#include<iomanip>
#include<cstring>
#include<stack>
#include<vector>
#include<string>
#include<map>
#include<cstdlib>
#include<queue>
#include<math.h>
#include<time.h>
#include<set>
#include<cstdio>
#include<stdio.h>
#include<algorithm>
using namespace std;
long long n,k,ans=-1,firstn,endn;
int main(){
	cin>>n>>k;
	long long mod=k*10;
	firstn=n%mod;
	endn=n;
    while(firstn!=endn%mod){
		ans++;
		endn*=n;
		cout<<endn<<endl;
		if(ans>100){
			cout<<-1;
			return 0;
		}
	}
	cout<<ans;
	return 0;
}