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>
  const long long mod = 1000000000 + 7;
  using namespace std;
  long long gcd(long long a, long long b) {
    if (b == 0) return a;
    return gcd(b, a % b);
  }
  long long fastPower(long long a, long long b) {
    if (b == 0) return 1;
    long long value = fastPower(a, b / 2);
    if (b % 2 == 0)
      return value * value;
    else
      return value * value * a;
  }
  long long fastPowerMod(long long x, long long y, long long mod) {
    if (y == 0) return 1 % mod;
    long long u = fastPowerMod(x, y / 2, mod);
    u = u * u % mod;
    if (y & 1) u = u * x % mod;
    return u;
  }
  int main() {
    long long t, n, m;
    cin >> t;
    while (t--) {
      cin >> n >> m;
      long long com, f, ans = 0;
      do {
        com = (long long)log2(m);
        f = fastPowerMod(2, com, mod);
        ans += fastPowerMod(n, com, mod);
        m -= f;
      } while (m != 0);
      cout << ans % mod << "\n";
    }
  }
  