Algorithm

A. Guess a number!
time limit per test
1 second
memory limit per test
256 megabytes
Problem link- https://codeforces.com/contest/416/problem/A
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).

Examples
input
Copy
4
>= 1 Y
< 3 N
<= -3 N
> 55 N
output
Copy
17
input
Copy
2
> 100 Y
< -100 Y
output
Copy
Impossible



 

Code Examples

#1 Code Example with C++ Programming

Code - C++ Programming

#include <bits/stdc++.h>

using namespace std;

int n, mn = -2e9, mx = 2e9;

int main() {
  cin >> n;

  string op;
  int num;
  char ans;
  for(int i = 0; i < n; ++i) {
    cin >> op >> num >> ans;

    if(op == ">") {
      if(ans == 'Y')
        mn = max(mn, num + 1);
      else
        mx = min(mx, num);
    }

    if(op == "<") {
      if(ans == 'Y')
        mx = min(mx, num - 1);
      else
        mn = max(mn, num);
    }

    if(op == ">=") {
      if(ans == 'Y')
        mn = max(mn, num);
      else
        mx = min(mx, num - 1);
    }

    if(op == "<=") {
      if(ans == 'Y')
        mx = min(mx, num);
      else
        mn = max(mn, num + 1);
    }
  }

  if(mn > mx)
    puts("Impossible");
  else {
    cout << mn << endl;
  }

  return 0;
}
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Input

x
–
+
cmd
4
>= 1 Y
< 3 N
<= -3 N
> 55 N

Output

x
–
+
cmd
17
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Demonstration

Codeforces Solution-Guess a number!-Solution in C, C++, Java, Python

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