/* -*- coding: utf-8 -*-
 *
 * 2927.cc:  No.2927 Reverse Polish  Equation - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_QN = 200000;

enum { X = -1, ADD = -2, MIN = -3, MAX = -4 };

/* typedef */

using ll = long long;

/* global variables */

int fs[MAX_QN];
ll as[MAX_QN];

/* subroutines */

ll calc(int qn, ll x) {
  int n = 0;
  ll a0, a1;
  for (int i = 0; i < qn; i++) {
    switch (fs[i]) {
    case X:
      as[n++] = x;
      break;
    case ADD:
      a0 = as[--n], a1 = as[--n];
      as[n++] = a0 + a1;
      break;
    case MIN:
      a0 = as[--n], a1 = as[--n];
      as[n++] = min(a0, a1);
      break;
    case MAX:
      a0 = as[--n], a1 = as[--n];
      as[n++] = max(a0, a1);
      break;
    default:
      as[n++] = fs[i];
      break;
    }
  }
  return as[0];
}

/* main */

int main() {
  int qn;
  ll y;
  scanf("%d%lld", &qn, &y);

  for (int i = 0; i < qn; i++) {
    char s[16];
    scanf("%s", s);

    fs[i] =
      (s[0] == 'X') ? X :
      (s[0] == '+') ? ADD :
      (s[1] == 'i') ? MIN :
      (s[1] == 'a') ? MAX :
      atoi(s);
  }

  ll x0 = -1, x1 = y + 1;
  while (x0 + 1 < x1) {
    ll x = (x0 + x1) / 2;
    if (calc(qn, x) >= y) x1 = x;
    else x0 = x;
  }

  if (calc(qn, x1) != y) puts("-1");
  else printf("%llu\n", x1);

  return 0;
}