/*
TASK:necklace
LANG:C++
*/
#define MAXLEN 25

#include <iostream>
#include <cstring>

using namespace std;

int n;
int a[6] = {0, 0, 1, 1, 3, 6};
char current[MAXLEN+5], prev[MAXLEN+5], number[MAXLEN+5];

int main()
{
    scanf("%d", &n);
    
    if(n<=5) { printf("%d\n", a[n]); return 0; }
    
    strcpy(prev,"2");
    strcpy(current,"3");
    strcpy(number,"6");
    
    for (int i=6; i<=n; i++)
        {
             int pren=0, len, j;
             char tmp[MAXLEN+5];
             strcpy(tmp,current);
             
             len=strlen(prev);
             for (j=0; j<len; j++)
                 {                      
                      pren+=(current[j]-'0')+(prev[j]-'0');
                      current[j]=pren%10+'0';
                      pren/=10;
                 }
             if (pren)
                {
                      if (current[len]=='\0') { current[len]+=pren+'0'; current[len+1]='\0'; }
                         else
                             {
                                          for (j=len; j<strlen(current) && pren; j++)
                                              {
                                                   pren+=current[j]-'0';
                                                   current[j]=pren%10+'0';
                                                   pren/=10;
                                              }
                                          if (pren) { current[j]+=pren+'0'; current[j+1]='\0'; }
                             }
                }
             
             pren=0;
             len=strlen(current);
             
             for (j=0; j<len; j++)
                 {                      
                      pren+=(number[j]-'0')+(current[j]-'0');
                      number[j]=pren%10+'0';
                      pren/=10;
                 }
             if (pren)
                {
                      if (number[len]=='\0') { number[len]+=pren+'0'; number[len+1]='\0'; }
                         else
                             {
                                          for (j=len; j<strlen(number) && pren; j++)
                                              {
                                                   pren+=number[j]-'0';
                                                   number[j]=pren%10+'0';
                                                   pren/=10;
                                              }
                                          if (pren) { number[j]+=pren+'0'; number[j+1]='\0'; }
                             }
                }
             
             strcpy(prev,tmp);
        }
    
    for (int i=strlen(number)-1; i>=0; i--)
        printf("%c", number[i]);
    
    printf("\n");
    
return 0;
}
