#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }


int L, R;

int main() {
  for (int numCases; ~scanf("%d", &numCases); ) { for (int caseId = 1; caseId <= numCases; ++caseId) {
    scanf("%d%d", &L, &R);
    ++R;
    
    vector<int> ans(R - L, 0);
    if (R - L == 1) {
      if (L == 1) {
        ans[0] = L;
      } else {
        ans = {};
      }
    } else if ((R - L) % 2 != 0) {
      if (L % 2 != 0) {
        // [odd, odd]
        ans[0] = L + 2;
        ans[1] = L + 0;
        ans[2] = L + 1;
        for (int i = 3; i < R - L; ++i) {
          ans[i] = L + 3 + ((i - 3) ^ 1);
        }
      } else {
        // [even, even]
        ans = {};
      }
    } else {
      for (int i = 0; i < R - L; ++i) {
        ans[i] = L + (i ^ 1);
      }
    }
    
    if (!ans.empty()) {
      for (int i = 0; i < R - L; ++i) {
        if (i) printf(" ");
        printf("%d", ans[i]);
      }
      puts("");
    } else {
      puts("-1");
    }
  }
#ifndef LOCAL
  break;
#endif
  }
  return 0;
}