#include <bits/stdc++.h>
// #pragma GCC optimize(2)
#ifndef ONLINE_JUDGE
    #define Debug
#endif
#define multiple_test 1
#define Memset(a,b) memset(a,b,sizeof(a))
#define dbg(x) cout<<#x<<" = "<<x<<endl
#define int int64_t
const int MAXN = 1e6, N = MAXN+10;
const int MOD = 1e9+7;
const int INF = 0x3f3f3f3f3f3f3f3fll;
using namespace std;

inline void solve() {
    int a,b,c,d; cin>>a>>b>>c>>d;
    int l = a+c, r = b+d;
    if(r-l >= 9) {
        cout<<"9\n";
        return;
    }
    auto calc = [](int x) {
        int res = 0;
        while(x) {
            res = max(res,x % 10);
            x /= 10;
        }
        return res;
    };
    int res = 0;
    for(int i=l;i<=r;i++) {
        res = max(res,calc(i));
    }
    cout<<res<<"\n";
}

signed main() {
#ifndef ONLINE_JUDGE
    freopen("in.txt","r",stdin);
    // freopen("out.txt","w",stdout);
    clock_t start_time = clock();
#else
    ios::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);
#endif 
    int t = 1; if(multiple_test) cin>>t;
    while(t--) {
        solve();
    }
#ifndef ONLINE_JUDGE
    cout<<"Used "<<(double)(clock()-start_time)<<" ms"<<endl;
#endif
    return 0;
}