#include <stdio.h>
#include <stdlib.h>
#define C 250
int d[1000][C+1];
add(int a[],int b[])
{
    int i,o;
    for(i=C; i>0; i--)
        a[i]+=b[i];
    o=0;
    for(i=C; i>0; 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;
    d[3][C]=3;
    for(i=4; i<=n; i++)
    {
        add(d[i],d[i-1]);
        add(d[i],d[i-2]);
    }
    i=0;
    while(d[n][i]==0)
        i++;
    while(i<=C)
        printf("%d",d[n][i++]);

    return 0;
}