#if __INCLUDE_LEVEL__ == 0

#include __BASE_FILE__

namespace {

void solve() {
  int la, ra, lb, rb;
  scan(la, ra, lb, rb);
  ++ra, ++rb;

  if (la + 10 <= ra || lb + 10 <= rb) {
    print(9);
  } else {
    int ans = -1;
    for (const int a : rep(la, ra)) {
      for (const int b : rep(lb, rb)) {
        int x = a + b;
        do {
          chmax(ans, x % 10);
        } while (x /= 10);
      }
    }

    print(ans);
  }
}

}  // namespace

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);

  int t;
  scan(t);
  while (t--) {
    solve();
  }
}

#else  // __INCLUDE_LEVEL__

#include <bits/stdc++.h>

template <class T, class U = T>
bool chmin(T& x, U&& y) {
  return y < x && (x = std::forward<U>(y), true);
}

template <class T, class U = T>
bool chmax(T& x, U&& y) {
  return x < y && (x = std::forward<U>(y), true);
}

template <class T>
concept Range = std::ranges::range<T> && !std::convertible_to<T, std::string_view>;

template <class T>
concept TupleLike = std::__is_tuple_like<T>::value && !Range<T>;

namespace std {

istream& operator>>(istream& is, Range auto&& r) {
  for (auto&& e : r) {
    is >> e;
  }
  return is;
}

istream& operator>>(istream& is, TupleLike auto&& t) {
  return apply([&](auto&... xs) -> istream& { return (is >> ... >> xs); }, t);
}

ostream& operator<<(ostream& os, Range auto&& r) {
  string_view sep = "";
  for (auto&& e : r) {
    os << exchange(sep, " ") << e;
  }
  return os;
}

ostream& operator<<(ostream& os, TupleLike auto&& t) {
  const auto f = [&](auto&... xs) -> ostream& {
    [[maybe_unused]] string_view sep = "";
    ((os << exchange(sep, " ") << xs), ...);
    return os;
  };
  return apply(f, t);
}

#define DEF_INC_OR_DEC(op) \
  auto& operator op(Range auto&& r) { \
    for (auto&& e : r) { \
      op e; \
    } \
    return r; \
  } \
  auto& operator op(TupleLike auto&& t) { \
    apply([](auto&... xs) { (op xs, ...); }, t); \
    return t; \
  }

DEF_INC_OR_DEC(++)
DEF_INC_OR_DEC(--)

#undef DEF_INC_OR_DEC

}  // namespace std

void scan(auto&&... xs) { std::cin >> std::tie(xs...); }
void print(auto&&... xs) { std::cout << std::tie(xs...) << '\n'; }

#define FWD(...) static_cast<decltype(__VA_ARGS__)&&>(__VA_ARGS__)

template <class F>
class fix {
 public:
  explicit fix(F f) : f_(std::move(f)) {}

  decltype(auto) operator()(auto&&... xs) const { return f_(std::ref(*this), FWD(xs)...); }

 private:
  F f_;
};

template <class T>
concept LambdaExpr = std::is_placeholder_v<std::remove_cvref_t<T>> != 0 ||
                     std::is_bind_expression_v<std::remove_cvref_t<T>>;

auto operator++(LambdaExpr auto&& x, int) {
  return std::bind([](auto&& x) -> decltype(auto) { return FWD(x)++; }, FWD(x));
}

auto operator--(LambdaExpr auto&& x, int) {
  return std::bind([](auto&& x) -> decltype(auto) { return FWD(x)--; }, FWD(x));
}

#define DEF_UNARY_OP(op) \
  auto operator op(LambdaExpr auto&& x) { \
    return std::bind([](auto&& x) -> decltype(auto) { return op FWD(x); }, FWD(x)); \
  }

DEF_UNARY_OP(++)
DEF_UNARY_OP(--)
DEF_UNARY_OP(+)
DEF_UNARY_OP(-)
DEF_UNARY_OP(~)
DEF_UNARY_OP(!)
DEF_UNARY_OP(*)
DEF_UNARY_OP(&)

#undef DEF_UNARY_OP

#define DEF_BINARY_OP(op) \
  template <class T1, class T2> \
    requires LambdaExpr<T1> || LambdaExpr<T2> \
  auto operator op(T1&& x, T2&& y) { \
    return std::bind([](auto&& x, auto&& y) -> decltype(auto) { return FWD(x) op FWD(y); }, \
                     FWD(x), FWD(y)); \
  }

DEF_BINARY_OP(+=)
DEF_BINARY_OP(-=)
DEF_BINARY_OP(*=)
DEF_BINARY_OP(/=)
DEF_BINARY_OP(%=)
DEF_BINARY_OP(^=)
DEF_BINARY_OP(&=)
DEF_BINARY_OP(|=)
DEF_BINARY_OP(<<=)
DEF_BINARY_OP(>>=)
DEF_BINARY_OP(+)
DEF_BINARY_OP(-)
DEF_BINARY_OP(*)
DEF_BINARY_OP(/)
DEF_BINARY_OP(%)
DEF_BINARY_OP(^)
DEF_BINARY_OP(&)
DEF_BINARY_OP(|)
DEF_BINARY_OP(<<)
DEF_BINARY_OP(>>)
DEF_BINARY_OP(==)
DEF_BINARY_OP(!=)
DEF_BINARY_OP(<)
DEF_BINARY_OP(>)
DEF_BINARY_OP(<=)
DEF_BINARY_OP(>=)
DEF_BINARY_OP(&&)
DEF_BINARY_OP(||)

#undef DEF_BINARY_OP

template <class T1, class T2>
  requires LambdaExpr<T1> || LambdaExpr<T2>
auto at(T1&& x, T2&& y) {
  return std::bind([](auto&& x, auto&& y) -> decltype(auto) { return FWD(x)[FWD(y)]; }, FWD(x),
                   FWD(y));
}

template <int I>
auto get(LambdaExpr auto&& x) {
  return std::bind([](auto&& x) -> decltype(auto) { return std::get<I>(FWD(x)); }, FWD(x));
}

inline auto rep(int l, int r) { return std::views::iota(std::min(l, r), r); }
inline auto rep(int n) { return rep(0, n); }
inline auto rep1(int l, int r) { return rep(l, r + 1); }
inline auto rep1(int n) { return rep(1, n + 1); }

using namespace std::literals;
using namespace std::placeholders;

namespace ranges = std::ranges;
namespace views = std::views;

using i64 = std::int64_t;

#endif  // __INCLUDE_LEVEL__