#include<fstream>
#include<cstring>
using namespace std;
ifstream fin("nunta.in");
ofstream fout("nunta.out");
short a[213],b[213],c[213];
int n,m,t,i,j;
int main(){
    fin>>n;
    n++;
    if(n<=2){
        fout<<1;
        return 0;
    }
    a[0]=a[1]=1;
    b[0]=b[1]=1;
    for(i=3;i<=n;i++){
        memset(c,0,sizeof(c));
        m=max(a[0],b[0]);
        c[0]=m;
        t=0;
        for(j=1;j<=m;j++){
            c[j]=a[j]+b[j]+t;
            t=c[j]/10;
            c[j]%=10;
        }
        if(t){
            c[++c[0]]=t;
            t=0;
        }
        memcpy(a,b,sizeof(b));
        memcpy(b,c,sizeof(c));
    }
    for(i=c[0];i>=1;i--){
        fout<<c[i];
    }
    return 0;
}