import java.util.Scanner;
import java.util.ArrayDeque;
import java.util.function.LongUnaryOperator;
class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int Q = sc.nextInt();
		long Y = sc.nextLong();
		ArrayDeque<LongUnaryOperator> deq = new ArrayDeque<>();
		while(Q-->0){
			String S = sc.next();
			if(S.equals("+")){
				LongUnaryOperator f1 = deq.pollLast();
				LongUnaryOperator f2 = deq.pollLast();
				LongUnaryOperator f = x -> f1.applyAsLong(x)+f2.applyAsLong(x);
				deq.add(f);
			}
			else if(S.equals("min")){
				LongUnaryOperator f1 = deq.pollLast();
				LongUnaryOperator f2 = deq.pollLast();
				LongUnaryOperator f = x -> Math.min(f1.applyAsLong(x),f2.applyAsLong(x));
				deq.add(f);
			}
			else if(S.equals("max")){
				LongUnaryOperator f1 = deq.pollLast();
				LongUnaryOperator f2 = deq.pollLast();
				LongUnaryOperator f = x -> Math.max(f1.applyAsLong(x),f2.applyAsLong(x));
				deq.add(f);
			}
			else if(S.equals("X")){
				LongUnaryOperator f = X -> X;
				deq.add(f);
			}
			else{
				long num = Long.parseLong(S);
				LongUnaryOperator f = X -> num;
				deq.add(f);
			}
		}
		LongUnaryOperator f = deq.pollFirst();
		long a = 0;
		long b = 10_000_000_000_001L;
		long inf = b;
		long ans = b;
		while(a-b<1){
			long c = a+b>>1;
			if(f.applyAsLong(c)<Y)
				a = c+1;
			else
				b = (ans=c)-1;
		}
		System.out.println(f.applyAsLong(ans)==Y?ans:-1);
	}
}