C++ Program to Find Fibonacci Numbers using Iteration

#include <cstring>
#include <iostream>
#include <cstdlib>
#define ll long long
using namespace std;
 
/* 
 * Iterative function to find Fibonacci Numbers 
 */
ll fibo_iter(int n)
{
    int previous = 1;
    int current = 1;
    int next = 1;
    for (int i = 3; i <= n; ++i) 
    {
        next = current + previous;
        previous = current;
        current = next;
    }
    return next;
}
/* 
 * Main
 */
int main()
{
    int n;
    while (1)
    {
        cout<<"Enter the integer n to find nth fibonnaci no.(0 to exit): ";
        cin>>n;
        if (n == 0)
            break;
        cout<<fibo_iter(n)<<endl;
    }
    return 0;
}

Output:
Enter the integer n to find nth fibonnaci no.(0 to exit): 1
1
Enter the integer n to find nth fibonnaci no.(0 to exit): 2
1
Enter the integer n to find nth fibonnaci no.(0 to exit): 3
2
Enter the integer n to find nth fibonnaci no.(0 to exit): 4
3
Enter the integer n to find nth fibonnaci no.(0 to exit): 5
5
Enter the integer n to find nth fibonnaci no.(0 to exit): 6
8
Enter the integer n to find nth fibonnaci no.(0 to exit): 7
13
Enter the integer n to find nth fibonnaci no.(0 to exit): 8
21
Enter the integer n to find nth fibonnaci no.(0 to exit): 9
34
Enter the integer n to find nth fibonnaci no.(0 to exit): 10
55
Enter the integer n to find nth fibonnaci no.(0 to exit): 0
 
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