#include<stdio.h>
int a[300],b[300],c[300],i,n;
void C(int a[],int b[]) {
    for(int i=0;i<=b[0];i++)
        a[i]=b[i];
}
void A(int a[],int b[],int c[]) {
    int i,t=0;
    for(i=1;i<=b[0]||i<=c[0]||t;i++,t/=10)
        a[i]=(t+=b[i]+c[i])%10;
    a[0]=i-1;
}
int main() {
    freopen("nunta.in","r",stdin),freopen("nunta.out","w",stdout),scanf("%d",&n),b[1]=2,c[1]=b[0]=c[0]=1;
    if(n>3) {
        n-=2;
        while(n--)
            A(a,b,c),C(c,b),C(b,a);
        for(i=a[0];i;i--)
            printf("%d",a[i]);
    }
    else
        printf("%d",n);
}