#include <stdio.h>
#include <stdlib.h>
#include <string.h>
extern int getchar_unlocked(void);
extern int putchar_unlocked(int);
#define gc(d)	(d)=getchar_unlocked()
#define	pc(d) putchar_unlocked(d)
#define REP(a,b) for(int a=0;a<(int)(b);++a)
static char *GETWORD(char* str) {char c;char *cp;cp=&str[0];gc(c);while(c!=EOF){if((c==' ')||(c=='\n'))break;*cp++=c;gc(c);}*cp='\0';return &str[0];}
#define GETLINE(str) do{char *p;fgets(str,sizeof(str),stdin);p=strchr(str,'\n');if(p)*p='\0';}while(0)
static int GETLINEINT(void) {char s[34];GETLINE(s);return atoi(s);}
static long GETLINELONG(void) {char s[34];GETLINE(s);return atol(s);}
#define MAX(a,b)	((a)>(b)?(a):(b))
// *********************
// *********************
int main( void ) {
	long	q= GETLINELONG();
	printf("%ld\n", (long)q+ MAX(q-3L,0) *4L);
	return 0;
}