#include <fstream>

using namespace std;

ifstream f("nunta.in");
ofstream g("nunta.out");

int a[500], b[500], c[500], n;

int main()
{
    f>>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-- ) g<<a[i];

    f.close(); g.close();
    return 0;
}