#include <iostream>
#include <fstream>
using namespace std;
ifstream f("nunta.in");
ofstream g("nunta.out");
const int MAXN = 215, BAZA = 10;
int N;
unsigned char F1[MAXN] = {1, 1},
                         F2[MAXN] = {1, 2},
                                    *M1 = F1, *M2 = F2, *AX;
void adunare(unsigned char A[],unsigned char B[])
{
    int T = 0;
    A[0] = A[0]>B[0]?A[0]:B[0];
    for(int i = 1; i <= A[0]; i++)
    {
        T += A[i]+B[i];
        A[i] = T % 10;
        T /= 10;
    }
    if(T > 0)
        A[++A[0]] = 1;
}
int main()
{   f>>N;
    if(N<=2)
        M2[1]=N;
    else
     for(int i=3;i<=N;i++)
     {
         adunare(M1,M2);
         swap(M1,M2);
     }
   for(int i=M2[0];i>=1;i--)
        g<<int(M2[i]);
    return 0;
}