#include <cstdio>
 
using namespace std;
 
int a[500], b[500], c[500], n;
 
int main()
{
    freopen("nunta.in", "r", stdin);
    freopen("nunta.out", "w", stdout);
 
    scanf("%d", &n);
    a[0]=1; a[1]=2;
    b[0]=1; b[1]=1;
 
    if (n==1)
    {
        printf("1\n"); return 0;
    }
 
    for (int j=3; j<=n; j++)
    {
        int t=0, i;
        for (i=0; i<=a[0]; i++) c[i]=a[i];
        for (i=1; i<=a[0] || i<=b[0] || t; i++, t/=10) a[i]=(t+=a[i]+b[i])%10;
 
        a[0]=i-1;
        for (i=0; i<=c[0]; i++) b[i]=c[i];
    }
 
    for ( int i=a[0]; i; i-- ) printf("%d", a[i]);
 
    return 0;
}