#include <iostream>

using namespace std;
int fib[33];

int f(int n)
{
    if(n==1 || n==2)
    {
        return 1;
    }
    if(fib[n] != -1) {
        return fib[n];
    }
    return fib[n] = f(n-2)+f(n-1);
}
int main()
{
    int n;
    cin>>n;
    for(int i = 0; i <= n; i++) {
        fib[i] = -1;
    }
    cout<<f(n);
    return 0;
}