#include <cstdio>

using namespace std;

int a[11],b[11],n;

void Aduna(int A[],int B[])
{
    int t=0,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;
}

int main()
{
    int i;
    freopen("nunta.in","r",stdin);
    scanf("%d",&n);
    a[0]=a[1]=1;
    b[0]=b[1]=1;
    for(i=3;i<=n+1;++i)
        if(i%2==0)
            Aduna(a,b);
        else
            Aduna(b,a);
    freopen("nunta.out", "w", stdout);
    if(n%2==1)
        for(i=a[0];i>=1;--i)
            printf("%d",a[i]);
    else
        for(i=b[0];i>=1;--i)
            printf("%d",b[i]);
    printf("\n");
    return 0;
}