description: Theofanis really likes sequences of positive integers, thus his teacher (Yeltsa Kcir) gave him a problem about a sequence that consists of only special numbers.
  
  Let's call a positive number special if it can be written as a sum of different non-negative powers of n. For example, for n = 4 number 17 is special, because it can be written as 4^0 + 4^2 = 1 + 16 = 17, but 9 is not.
  
  Theofanis asks you to help him find the k-th special number if they are sorted in increasing order. Since this number may be too large, output it modulo 10^9+7.
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 10^4) — the number of test cases.
  
  The first and only line of each test case contains two integers n and k (2 ≤ n ≤ 10^9; 1 ≤ k ≤ 10^9).
  
  Output
  
  For each test case, print one integer — the k-th special number in increasing order modulo 10^9+7.
  
  Example
  
  Input
  
  
  3
  3 4
  2 12
  105 564
  
  
  Output
  
  
  9
  12
  3595374
  
  Note
  
  For n = 3 the sequence is [1,3,4,9...]
solution: #include <bits/stdc++.h>
  using namespace std;
  const int N = 30 + 1;
  const int mod = 1e9 + 7;
  int bigmod(int a, int b) {
    int ans = 1;
    while (b > 0) {
      if (b & 1) {
        ans = (ans * 1ll * a) % mod;
      }
      a = (a * 1ll * a) % mod;
      b >>= 1;
    }
    return ans;
  }
  inline int add(int x, int y) { return (x + y >= mod ? x + y - mod : x + y); }
  inline int sub(int x, int y) { return (x - y < 0 ? x - y + mod : x - y); }
  inline int gun(int x, int y) { return ((x * 1ll * y) % mod); }
  inline int vag(int x, int y) { return (x * 1ll * bigmod(y, mod - 2)) % mod; }
  int koto[N];
  int koto2[N];
  void TEST_CASES() {
    int n, k;
    cin >> n >> k;
    koto2[0] = 1;
    for (int i = 1; i < N; i++) {
      koto2[i] = gun(koto2[i - 1], n);
    }
    int ans = 0;
    while (k != 0) {
      for (int i = 0; i < N; i++) {
        if (koto[i] > k) {
          i--;
          ans = add(ans, koto2[i]);
          k -= koto[i];
          break;
        }
      }
    }
    cout << ans << "\n";
  }
  int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    koto[0] = 1;
    for (int i = 1; i < N; i++) {
      koto[i] = (1 << (i));
    }
    int t = 1;
    cin >> t;
    while (t--) {
      TEST_CASES();
    }
    return 0;
  }
  