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 = 4e5 + 5;
  int MOD = 1e9 + 7;
  long long fast_power(long long base, long long power) {
    long long result = 1;
    while (power > 0) {
      if (power % 2 == 1) {
        result = (result * base) % MOD;
      }
      base = (base * base) % MOD;
      power = power / 2;
    }
    return result;
  }
  int n, k;
  bool get(int index) {
    long long get = fast_power(2, index);
    if (k < get) return 0;
    if (get == 1) return k % 2;
    return ((k / get) % 2);
  }
  int main() {
    int test;
    cin >> test;
    while (test--) {
      cin >> n >> k;
      long long sum = 0;
      for (int i = 0; i <= 30; ++i) {
        if ((k >> i) & 1) {
          sum = (sum % MOD + fast_power(n, i) % MOD) % MOD;
        }
      }
      cout << sum % MOD << "\n";
    }
    return 0;
  }
  