#include <cstdio>

void suma(int a[], int b[]){
    int i,t=0;
    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 a[100005], b[100005];

int main(){

    freopen("nunta.in","r",stdin);
    freopen("nunta.out","w",stdout);

    int n,i;

    scanf("%d",&n);

    a[0]=1;
    a[1]=0;

    b[0]=1;
    b[1]=1;

    for(i=2; i<=n+1; i+=2){
        suma(a,b);
        suma(b,a);
    }

    if(n%2!=0)
        for(i=a[0]; i>0; i--)
            printf("%d",a[i]);
    else
        for(i=b[0]; i>0; i--)
            printf("%d",b[i]);

}