Semi (actual submission)

Challenge.java

public class Problem1 {
	static enum Oper {
		PLUS,
		MINUS
	}
	public static void main(String[] args) {
		Oper lastOp = null;
		Integer lastNum = null;
		Integer res = null;
		for (String s : Input.read().split(" ")) {
			System.out.println("" + s + "    " + res);
			int n = num(s);
			if (n > 0) {
				if (res == null) {
					res = n;
					lastNum = n;
					continue;
				}
				if (lastOp != null) {
					switch (lastOp) {
						case PLUS:
							res += lastNum;
							break;
						case MINUS:
							res -= lastNum;
							break;
						default:
						// ??
					}
				}
				lastNum = n;
			}
			else if (s.equals("plus")) {
				lastOp = Oper.PLUS;
			}
			else if (s.equals("minus")) {
				lastOp = Oper.MINUS;
			}
			else {
				// ???
			}
		}

		Output.write("" + res);
	}
	static int num(String input) {
		if (input.equals("one")) return 1;
		if (input.equals("two")) return 2;
		if (input.equals("three")) return 3;
		if (input.equals("four")) return 4;
		if (input.equals("five")) return 5;
		if (input.equals("six")) return 6;
		if (input.equals("seven")) return 7;
		if (input.equals("eight")) return 8;
		if (input.equals("nine")) return 9;
		return -1;
	}
}