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: 
  import java.io.*;
  import java.util.Random;
  import java.util.StringTokenizer;
  
  public class Main {
      static int mod = 1000000007;
      static InputReader sc = new InputReader(System.in);
      static PrintWriter out = new PrintWriter(System.out);
      public static void main(String[] args) throws IOException {
          int t = sc.nextInt();
          while(t -- > 0){
              int n = sc.nextInt();
              int k = sc.nextInt();
  
              int x = 1;
              int L = 0;
              while((x << L) <= k){
                  L++;
              }
              L--;
  
              long[] exponent = new long[L + 1];
              for(int i = 0 ; i <= L; i++){
                  int v = i / 2;
                  exponent[i] = 1;
                  if(i % 2 == 1) {
                      exponent[i] = n;
                  }
                  exponent[i] = (exponent[i] * ((exponent[v] * exponent [v] ) % mod)) % mod;
              }
  
              int sum = 0;
              while(k > 0){
                  if((x << L) <= k ){
                      sum = (sum + (int)exponent[L])%mod;
                      k -= (x << L);
                  }
                  L--;
              }
              System.out.println(sum);
  
  
          }
  
          out.flush();
          out.close();
      }
  
  
      private static class InputReader {
          public BufferedReader reader;
          public StringTokenizer tokenizer;
  
          public InputReader(InputStream stream) {
              reader = new BufferedReader(new InputStreamReader(stream), 32768);
              tokenizer = null;
          }
  
          public String next() {
              while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                  try {
                      tokenizer = new StringTokenizer(reader.readLine());
                  } catch (IOException e) {
                      throw new RuntimeException(e);
                  }
              }
              return tokenizer.nextToken();
          }
  
          public int nextInt() {
              return Integer.parseInt(next());
          }
  
          public long nextLong() {
              return Long.parseLong(next());
          }
  
          public double nextDouble(){ return Double.parseDouble(next()); }
      }
  
      void shuffleArray(long[] arr){
          int n = arr.length;
          Random rnd = new Random();
          for(int i=0; i<n; ++i){
              long tmp = arr[i];
              int randomPos = i + rnd.nextInt(n-i);
              arr[i] = arr[randomPos];
              arr[randomPos] = tmp;
          }
      }
  
      static class Pair<K, V>{
  
          K key;
          V value;
          public Pair(K key, V value){
              this.key = key;
              this.value = value;
          }
      }
  
  }
  