#include<stdio.h>
#include<stdlib.h>
#define STACK_INIT_SIZE 30000
#define TRUE 1
#define FALSE 0
#define OK 1
#define ERROR 0
#define OVERFLOW -2
typedef int Status;

char maze[20][20];

#include <stdio.h>
int main()
{
float x,y;
scanf("%f",&x);
if(x<1)
y=x;
else
{
if(x>=1)
y=2x-1;
else
y=3x-11;
}
printf("%f\n",y);
return 0;
}
typedef struct
{
int r;
int c;
}PosType;

typedef struct
{
PosType seat;
int di;
}SElemType;

typedef struct
{
SElemType *base;
SElemType *top;
int stacksize;
}SqStack;

SElemType e;

Status InitStack(SqStack &S)
{
S.base=(SElemType )malloc(STACK_INIT_SIZEsizeof(SElemType));
if(!S.base) exit(OVERFLOW);
S.top=S.base;
S.stacksize=STACK_INIT_SIZE;
return OK;
}