#include <cstdio>
#include <cstring>
#define nmax 210
unsigned char a[nmax+1],b[nmax+1],c[nmax+1];
short n,m,i;

int main()
{
    freopen("nunta.in","r",stdin);
    freopen("nunta.out","w",stdout);
    scanf("%d",&n);
    a[nmax]=1;b[nmax]=2;m=nmax;
    for(;n>2;n--){
        c[nmax]=b[nmax]+a[nmax];
        for(i=nmax-1;i>=m;i--)
            c[i]=b[i]+a[i]+c[i+1]/10,c[i+1]%=10;
        if(c[m]/10) {
            m--;
            c[m]=c[m+1]/10;
            c[m+1]%=10;
        }
        memcpy(a,b,sizeof(a));
        memcpy(b,c,sizeof(a));}
        if(n==2)
            memcpy(a,b,sizeof(a));
        i=0;
        for(i=m;i<=nmax;i++)
        printf("%d",a[i]);
    return 0;
 }