lab1.2 c++

#include <iostream>

using namespace std;

int main()
{
    int a, b, n = 0;
    a = 1;
    b = 1;
    cout << "The program will calculate the n-th term of the Fibonacci series.\n";
    bool IsCorrect;
    cout << "Enter the Fibonacci series member number: ";
    do
    {
        IsCorrect = false;
        cin >> n;
        if ((cin.fail()) or (n < 0) or (n == 0))
        {
            IsCorrect = true;
            cout << "Incorrect value. Enter the number: ";
        }
        cin.clear();
        while (cin.get() != '\n');
    } while (IsCorrect);
    for (int i = 2; i < n; i++)
    {
        b = a + b;
        a = b - a;
    }
    cout << b;

    return 0;
}