import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedList;

class Solution {

	public int evaluate(String expression) {
		HashMap<String, Integer> bl = new HashMap<>();
		int res = help(expression, bl);
		return res;
	}

	private Integer help(String ex, HashMap<String, Integer> bl) {
		if (ex.startsWith("(")) {
			String tmp = ex.substring(1, ex.length() - 1);
			String[] els = deal(tmp);
			if (els[0].equals("let")) {
				for (int i = 1; i < els.length - 1; i += 2) {
					bl.put(els[i], help(els[i + 1], new HashMap<>(bl)));
				}
				return help(els[els.length - 1], new HashMap<>(bl));
			} else if (els[0].equals("add")) {
				return help(els[1], new HashMap<>(bl)) + help(els[2], new HashMap<>(bl));
			} else {
				return help(els[1], new HashMap<>(bl)) * help(els[2], new HashMap<>(bl));
			}
		} else {
			if (Character.isDigit(ex.charAt(0)) || ex.charAt(0) == '-') {
				return Integer.parseInt(ex);
			} else {
				return bl.get(ex);
			}
		}
	}

	private String[] deal(String tmp) {
		ArrayList<String> ret = new ArrayList<>();
		String[] els = tmp.split(" ");
		for (int i = 0; i < els.length;) {
			if (!els[i].startsWith("(")) {
				ret.add(els[i++]);
			} else {
				StringBuilder el = new StringBuilder(els[i]);
				LinkedList<String> stack = new LinkedList<>();
				stack.addFirst(els[i++]);
				while (!stack.isEmpty() && i < els.length) {
					if (els[i].startsWith("(")) {
						stack.addFirst(els[i]);
					}
					int k = els[i].length() - 1;
					while (k >= 0) {
						if (els[i].charAt(k--) != ')')
							break;
						stack.removeFirst();
					}
					el.append(" ").append(els[i++]);
				}
				ret.add(el.toString());
			}
		}
		return ret.toArray(new String[ret.size()]);
	}
}