#include <iostream>
#include <fstream>
using namespace std;
ifstream f("nunta.in");
ofstream g("nunta.out");
unsigned char f1[212] = {1, 1}, f2[212] = {1, 2};
void adun(unsigned char f1[], unsigned char f2[])
{
    int t = 0;
    for(int i = 1; i <= f2[0] ; i++)
    {
        t += f1[i] + f2[i];
        f1[i] = t % 10;
        t /= 10;
    }
    f1[0] = f2[0];
    while(t > 0)
    {
        f1[++f1[0]] = t % 10;
        t /= 10;
    }
}
void afisare(unsigned char a[])
{
    for(int i = a[0]; i > 0; i--)
        g << int(a[i]);
}
void fib(int N)
{
    if(N <= 2)g << N;
    else
    {
        unsigned char *p1 = &f1[0], *p2 = &f2[0], *px;
        for(int i = 3; i <= N; i++)
        {
            adun(p1, p2);
            px = p1;
            p1 = p2;
            p2 = px;
        }
        afisare(p2);
    }
}

int main()
{
    int N;
    f >> N;
    fib(N);
    return 0;
}