import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayDeque;
import java.util.Deque;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] sa = br.readLine().split(" ");
		int q = Integer.parseInt(sa[0]);
		long y = Long.parseLong(sa[1]);
		sa = br.readLine().split(" ");
		br.close();

		boolean flg = false;
		for (int i = 0; i < q; i++) {
			if (sa[i].equals("X")) {
				flg = true;
			}
		}
		if (!flg) {
			System.out.println(-1);
			return;
		}

		long ok = 100000000000000L;
		long ng = -1;
		while (Math.abs(ok - ng) > 1) {
			long mid = (ok + ng) / 2;
			long val = calc(sa, mid);
			if (val >= y) {
				ok = mid;
			} else {
				ng = mid;
			}
		}
		if (calc(sa, ok) == y) {
			System.out.println(ok);
		} else {
			System.out.println(-1);
		}
	}

	static long calc(String[] sa, long mid) {
		Deque<String> que = new ArrayDeque<>();
		for (int i = 0; i < sa.length; i++) {
			if (sa[i].equals("+")) {
				long v1 = Long.parseLong(que.pop());
				long v2 = Long.parseLong(que.pop());
				que.push(String.valueOf(v1 + v2));

			} else if (sa[i].equals("min")) {
				long v1 = Long.parseLong(que.pop());
				long v2 = Long.parseLong(que.pop());
				que.push(String.valueOf(Math.min(v1, v2)));

			} else if (sa[i].equals("max")) {
				long v1 = Long.parseLong(que.pop());
				long v2 = Long.parseLong(que.pop());
				que.push(String.valueOf(Math.max(v1, v2)));

			} else if (sa[i].equals("X")) {
				que.push(String.valueOf(mid));

			} else {
				que.push(String.valueOf(sa[i]));
			}
		}
		return Long.parseLong(que.pop());
	}
}