std::move_backward in C++

Moves the elements in the range [first,last] starting from the end into the range terminating at result.
The function begins by moving *(last-1) into *(result-1), and then follows backward by the elements preceding these, until first is reached (and including it).
Template :

BidirectionalIterator2 move_backward (BidirectionalIterator1 first,
                                      BidirectionalIterator1 last,
                                      BidirectionalIterator2 result);

result
Bidirectional iterator to the past-the-end position in the destination sequence.
This shall not point to any element in the range [first,last].

Return Type :
An iterator to the first element of the destination sequence where elements
have been moved.

Examples:

Input :
vec1 contains : 3 4 5 7 8
vec2 contains : 8 9 6 2 4 7
Output :
arr2 contains : 8 9 6 5 7 8
/*3 elements from 3rd position of vector vec1 moved to starting 4th position of vec2*/

// CPP program to illustrate
// std::move and std::move_backward
// STL library functions
#include<bits/stdc++.h>

// Driver code
int main()
{
    std :: vector <int> vec1 {1, 2, 3, 4, 5};
    std :: vector <int> vec2 {7, 7, 7, 7, 7};

    // Print elements
    std :: cout << "Vector1 contains :";
    for(int i = 0; i < vec1.size(); i++)
        std :: cout << " " << vec1[i];
    std :: cout << "\n";

    // Print elements
    std :: cout << "Vector2 contains :";
    for(unsigned int i = 0; i < vec2.size(); i++)
        std :: cout << " " << vec2[i];
    std :: cout << "\n\n";


    // std :: move_backward function
    std :: move_backward (vec2.begin(), vec2.begin() + 3, vec1.begin() + 3);

    // Print elements
    std :: cout << "Vector1 contains after std::move_backward function:";
    for(unsigned int i = 0; i < vec1.size(); i++)
        std :: cout << " " << vec1[i];
    std :: cout << "\n";

    return 0;
}

Output:

Vector1 contains : 1 2 3 4 5
Vector2 contains : 7 7 7 7 7

Vector1 contains after std::move_backward function: 7 7 7 4 5