#include<bits/stdc++.h>
using namespace std;

unsigned long long int fibonacci(unsigned long long int number)
{
    unsigned long long int sum;
    if(number == 0)
    {
        return 0;
    }
    else if(number == 1)
    {
        return 1;
    }
    else
    {
        sum = fibonacci(number - 1) + fibonacci(number - 2);

        return sum;
    }
}

int main()
{
    unsigned long long int input, output;
    cin>>input;

    for(int i = 0; i<input; i++)
    {
        output = fibonacci(input);
    }

    cout<<output;
}