#include<stdio.h>
long long int num(char s[])
{
	long long int res = 0, i;
	for (i = 0; s[i] != '\0'; i++)
		res = 10 * res + s[i] - '0';
	return res;
}
long long int q;
char s[200005][16];
long long int a[200005];
long long int cal(long long int x)
{
	long long int aa, i;
	aa = 0;
	for (i = 0; i < q; i++)
	{
		if (s[i][0] == 'X')
		{
			a[aa] = x;
			aa++;
		}
		else if (s[i][0] == '+')
		{
			aa--;
			a[aa - 1] += a[aa];
		}
		else if (s[i][1] == 'a')
		{
			aa--;
			if (a[aa - 1] < a[aa])
				a[aa - 1] = a[aa];
		}
		else if (s[i][1] == 'i')
		{
			aa--;
			if (a[aa - 1] > a[aa])
				a[aa - 1] = a[aa];
		}
		else
		{
			a[aa] = num(s[i]);
			aa++;
		}
	}
	return a[0];
}
int main()
{
	long long int y;
	scanf("%lld %lld", &q, &y);
	long long int i;
	for (i = 0; i < q; i++)
		scanf("%s", s[i]);
	long long int min, mid, max;
	min = -1;
	max = y + 1;
	while (max - min > 1)
	{
		mid = (max + min) / 2;
		if (cal(mid) < y)
			min = mid;
		else
			max = mid;
	}
	if (cal(max) != y)
		max = -1;
	printf("%lld\n", max);
	return 0;
}