UVa 1200 - A DP Problem

// UVa 1200 - A DP Problem

import java.util.Scanner;

public class Main {

	public static class Expression {
		public int coeficient;
		public int constant;
	}
	
	private static Expression parse(String str){
		Expression exp = new Expression();
		exp.constant = 0;
		exp.coeficient = 0;
		int number = 0, sign = 1;
		boolean x = false, numberSeen = false;
		for (int i=0; i<str.length(); i++){
			char ch = str.charAt(i);
			if (ch >= '0' && ch <= '9'){
				number = number*10 + (str.charAt(i) - '0');
				numberSeen = true;
			}
			else if (ch == '-' || ch == '+'){
				// reboot
				if (numberSeen == false && i != 0)
					number = 1;
				if (x)
					exp.coeficient += sign * number;
				else
					exp.constant += sign * number;
				x = false;
				number = 0;
				numberSeen = false;
				sign = ch == '+' ? 1 : -1;
			}
			else if (ch == 'x' || ch == 'X'){
				x = true;
			}
		}
		// reboot
		if (numberSeen == false)
			number = 1;
		if (x)
			exp.coeficient += sign * number;
		else
			exp.constant += sign * number;
		return exp;
	}

	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		int cases = scanner.nextInt();
		scanner.nextLine();

		for (; cases > 0; cases--) {
			String line = scanner.nextLine();
			int equal = line.indexOf("=");
			String left = line.substring(0, equal);
			String right = line.substring(equal+1);
			
			Expression leftExp = parse(left);
			Expression rightExp = parse(right);
			
			int coeficient = leftExp.coeficient - rightExp.coeficient;
			int constant = rightExp.constant - leftExp.constant;
			
			if (coeficient == 0 && constant == 0)
				System.out.println("IDENTITY");
			else if (coeficient == 0)
				System.out.println("IMPOSSIBLE");
			else
				System.out.println((int)Math.floor( ((double)constant) / coeficient ) );
		}
	}

}