#include <stdio.h>
#include <stdlib.h>
#define C 250
char d[3][C+1];
void add(char a[],char b[])
{
    int i,o=0;
    for(i=C; i>0; i--)
    {
        a[i]+=b[i];
        a[i]+=o;
        o=a[i]/10;
        a[i]%=10;
    }
}
int main()
{
    int n,i;
    freopen("nunta.in","r",stdin);
    freopen("nunta.out","w",stdout);
    scanf("%d",&n);
    d[1][C]=1;
    d[2][C]=2;
    for(i=3; i<=n; i++)
    {
        for(int j=0; j<=C; j++)
            d[i%3][j]=0;
        add(d[i%3],d[(i-1)%3]);
        add(d[i%3],d[(i-2)%3]);
    }
    i=0;
    while(d[n%3][i]==0)
        i++;
    while(i<=C)
        printf("%d",d[n%3][i++]);

    return 0;
}