文件目录

#include <iostream>
using namespace std;
int main()
{
    int k;
    cin >> k;
    int a = 1;
    int b = 1;
    int c = 1;
    for (int i = 3; i <= k; i++)
    {
        a = b;
        b = c;
        c = a + b;
    }
    cout << c;
    return 0;
}