Guess a number!（判断简单题）

A TV show called "Guess a number!" is gathering popularity. The whole Berland, the old and the young, are watching the show.

The rules are simple. The host thinks of an integer y and the participants guess it by asking questions to the host. There are four types of acceptable questions:

• Is it true that y is strictly larger than number x?
• Is it true that y is strictly smaller than number x?
• Is it true that y is larger than or equal to number x?
• Is it true that y is smaller than or equal to number x?

On each question the host answers truthfully, "yes" or "no".

Given the sequence of questions and answers, find any integer value of y that meets the criteria of all answers. If there isn't such value, print "Impossible".

Input

The first line of the input contains a single integer n (1 ≤ n ≤ 10000) — the number of questions (and answers). Next n lines each contain one question and one answer to it. The format of each line is like that: "sign x answer", where the sign is:

• ">" (for the first type queries),
• "<" (for the second type queries),
• ">=" (for the third type queries),
• "<=" (for the fourth type queries).

All values of x are integer and meet the inequation  - 109 ≤ x ≤ 109. The answer is an English letter "Y" (for "yes") or "N" (for "no").

Consequtive elements in lines are separated by a single space.

Output

Print any of such integers y, that the answers to all the queries are correct. The printed number y must meet the inequation  - 2·109 ≤ y ≤ 2·109. If there are many answers, print any of them. If such value doesn't exist, print word "Impossible" (without the quotes).

Sample test(s)

input

4>= 1 Y< 3 N<= -3 N> 55 N

output

17

input

2> 100 Y< -100 Y

output

Impossible

这道题并不难，可是卡了我一个多小时，思维能力还是有待提高啊！！！

#include<stdio.h>#include<string.h>#define M 2000000000#define N -2000000000//#include<algorithm>//using namespace std;//int maxx[10005],minn[10005];int main(){    int n;    while(~scanf("%d",&n))    {        char str[5];        int x,i,y,min,max,q=0,k=0;        min=N;        max=M;        char op;        for(int i=0;i<n;i++)        {            scanf("%s %d %c",str,&x,&op);            if(!strcmp(">",str))            {                if(op=='Y')                {                    if(min<=x)                    {                        min=x+1;                    }                }                else                {                    if(max>=x)                    {                        max=x;                    }                }            }            else if(!strcmp(">=",str))            {                if(op=='Y')                {                    if(min<x)                    {                        min=x;                    }                }                else                {                    if(max>x)                    {                        max=x-1;                    }                }            }            else if(!strcmp("<",str))            {                if(op=='Y')                {                    if(max>=x)                    {                        max=x-1;                    }                }                else                {                    if(min<=x)                    {                        min=x;                    }                }            }            else if(!strcmp("<=",str))            {                if(op=='Y')                {                    if(max>x)                         max=x;                }                else                {                    if(min<x)                    {                        min=x+1;                    }                }            }        }        if(min>max)        printf("Impossible\n");        else        printf("%d\n",min);    }    return 0;}