#include<bits/stdc++.h>
using namespace std;
const int N=1000010;
typedef long long LL;
LL a,b,c,d,n,m,idx,ans,e[N],ne[N],h[N],l1,l2,r1,r2,x1,x2,y3,y2;
void init(int x1,int x2,int y3,int y2)
{
    if(x2<x1) x2+=10;
    if(y2<y3) y2+=10;
    for(int i=x1;i<=x2;i++)
    {
        for(int j=y3;j<=y2;j++)
        {
            a=i%10+j%10;
            ans=max(a%10,ans);
        }
    }
}
void solve()
{
    ans=0;
    cin>>l1>>r1>>l2>>r2;a=1;
    for(LL i=1;i<=10;i++)
    {
        if(r1-l1>=10)
        {
            x1=0,x2=9;
        }
        else
        {
            x1=l1%10;
            x2=x1+r1-l1;
        }
        if(r2-l2>=10)
        {
            y3=0,y2=9;
        }
        else
        {
            y3=l2%10;
            y2=y3+r2-l2;
        }
        //cout<<x1<<" "<<x2<<" "<<y3<<" "<<y2<<endl;
        init(x1,x2,y3,y2);
        l1/=10;l2/=10;r1/=10;r2/=10;
    }
    cout<<ans<<endl;
}
int main()
{
    LL N=1;
    cin>>N;
    while(N--)
    {
        solve();
    }
    return 0;
}