#include<bits/stdc++.h>
using namespace std;
#define x first
#define y second
typedef long double f128;
typedef long long i64;
typedef unsigned long long u64;
typedef pair<int, int> PII;
const int INF = 0x3f3f3f3f,mod = 1e9 + 7;
const i64 inf = 2e18;
inline int read()
{
    char c = getchar();
    int x = 0,s = 1;
    while(c < '0' || c > '9')
    {
        if (c == '-')
            s = -1;
        c = getchar();
    }
    while (c >= '0' && c <= '9')
    {
        x = x * 10 + c - '0';
        c = getchar();
    }
    return x * s;
}
//解答------------------------------------------------------------

int find (i64 x)
{
    i64 cnt = 0;
    while (x)
    {
        cnt = max (cnt,x % 10);
        x /= 10;
    }
    return (int)cnt;
}

void solve()
{
    i64 la,ra,lb,rb;
    cin >> la >> ra >> lb >> rb;
    i64 ll = ra - la,rr = rb - lb;
    if (rr >= 9 || ll >= 9)
    {
        cout << 9 << endl;
        return;
    }
    else
    {
        int ans = 0;
        for (i64 i = la;i <= ra;i++)
          for (i64 j = lb;j <= rb;j++)
          {
            ans = max (ans,find (i + j));
          }
          cout << ans <<endl;
    }
    
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int T = 1;
    cin >> T;
    while (T --)
        solve();
    return 0;
}