Algorithms and Data Structures

  • Profound Academy

    • Status
      • 1
        Implementation
      • 2
        Bitwise operations
      • 3
        Prefix Sums
      • 4
        Sliding window / Two pointers
      • 5
        Modular Arithmetic
      • 6
        Number Theory
      • 7
        Binary Search
      • 8
        Basic Sorting
      • 9
        Greedy Algorithms
      • 10
        Basic Dynamic Programming
      • 11
        Recursion
      • 12
        Linked LIst
      • 13
        Queue & Stack
      • 14
        Binary tree + BST
      • 15
        Divide & Conquer + Advanced Sorting
      • 16
        Heap
      • 17
        Hashing
      • 18
        Graph Representation
      • 19
        BFS

    • Number of bit-strings

    Given an integer n, you are asked to calculate the number of different bit-strings of length n. As the resulting number might be too big, the output should contain the number of bit-strings modulo (1000000007).

    Input

    The input contains a single integer n (1 ≤ n ≤ ).

    Output

    The program should print the number of bit-strings of length n modulo .

    Examples

    Input
    Output
    3
    8
    2
    4

    Explanation

    1. 3: 000, 001, 010, 011, 100, 101, 110, 111
    1. 2: 00, 01, 10, 11
     

    Constraints

    Time limit: 1 seconds

    Memory limit: 512 MB

    Output limit: 1 MB

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