#include<bits/stdc++.h>
using namespace std;
inline int read() {
    int x = 0, k = 1; char ch = getchar();
    for (; ch < 48 || ch > 57; ch = getchar()) k ^= (ch == '-');
    for (; ch >= 48 && ch <= 57; ch = getchar()) x = x * 10 + (ch ^ 48);
    return k ? x : -x;
}
inline int solve(int x) {
    int Max = 0;
    for (int y = x; y > 0; ) {
        Max = max(Max, y % 10);
        y = y / 10;
    }
    return Max;
}
int l1, r1, l2, r2;
int main() {
    for (int T = read(); T--; ) {
        l1 = read(), r1 = read(), l2 = read(), r2 = read();
        int l = l1 + l2;
        int r = r1 + r2;
        int Max = 0;
        if (r - l + 1 >= 10) printf("9\n");
        else {
            for (int i = l; i <= r; i++)
                Max = max(Max, solve(i));
            printf("%d\n", Max);
        }
    }
}