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#include<bits/stdc++.h>
#define INF 0x3f3f3f3f
#define LL long long
#define ULL unsigned long long
#define bug(x) cout<<"bug-----"<<x<<endl
#define R(i,n) for(int i = 0; i < n; i++)
using namespace std;
const int mod= 1e9+7;
const int maxn = 100 +10;
int main(){
    //freopen("C:\\Users\\admin\\Desktop\\1.in","r",stdin);
    //freopen("C:\\Users\\admin\\Desktop\\1.out","w",stdout);
    std::ios::sync_with_stdio(false);
    int T;
    cin>>T;
    while(T--)
    {
        LL x,ans=1,k,flag=1;
        cin>>x>>k;
        if((x%2==0&&k%2==0)||(x%2==1&&k%2==1))
        {
            if(k==1)
                cout<<x<<endl;
            else
            {
                for(int i=x-2;i>0;i=i-2)
                {
                    ans*=i;
                    if(ans%10==k)
                    {
                        cout<<i-2<<endl;
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