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