CodeForces 416A Guess a number!

链接：http://codeforces.com/problemset/problem/416/A

Guess a number!

time limit per test：1 second

memory limit per test：256 megabytes

input：standard input

output：standard output

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

直接模拟，附上AC代码：

#include <iostream>
#include <cstdio>
#include <string>
#include <cmath>
#include <iomanip>
#include <ctime>
#include <climits>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <queue>
#include <vector>
#include <set>
#include <map>
//#pragma comment(linker, "/STACK:102400000, 102400000")
using namespace std;
typedef unsigned int li;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
const double pi = acos(-1.0);
const double e = exp(1.0);
const double eps = 1e-8;
int n, x;
char sign[5], answer;

int main()
{
ios::sync_with_stdio(false);
while (~scanf("%d", &n))
{
int maxy = 2000000000;
int miny = -2000000000;
while (n--)
{
scanf("%s%d %c", sign, &x, &answer);
if (!strcmp(">", sign))
{
if (answer == 'Y')
miny = max(miny, x+1);
else
maxy = min(maxy, x);
}
else if (!strcmp(">=", sign))
{
if (answer == 'Y')
miny = max(miny, x);
else
maxy = min(maxy, x-1);
}
else if (!strcmp("<", sign))
{
if (answer == 'Y')
maxy = min(maxy, x-1);
else
miny = max(miny, x);
}
else
{
if (answer == 'Y')
maxy = min(maxy, x);
else
miny = max(miny, x+1);
}
}
if (miny > maxy)
printf("Impossible\n");
else
printf("%d\n", miny);
}
return 0;
}