import macros;macro ImportExpand(s:untyped):untyped = parseStmt($s[2])
ImportExpand "cplib/tmpl/sheep.nim" <=== "when not declared CPLIB_TMPL_SHEEP:\n    const CPLIB_TMPL_SHEEP* = 1\n    {.warning[UnusedImport]: off.}\n    {.hint[XDeclaredButNotUsed]: off.}\n    import algorithm\n    import sequtils\n    import tables\n    import macros\n    import math\n    import sets\n    import strutils\n    import strformat\n    import sugar\n    import heapqueue\n    import streams\n    import deques\n    import bitops\n    import std/lenientops\n    import options\n    #入力系\n    proc scanf(formatstr: cstring){.header: \"<stdio.h>\", varargs.}\n    proc getchar(): char {.importc: \"getchar_unlocked\", header: \"<stdio.h>\", discardable.}\n    proc ii(): int {.inline.} = scanf(\"%lld\\n\", addr result)\n    proc lii(N: int): seq[int] {.inline.} = newSeqWith(N, ii())\n    proc si(): string {.inline.} =\n        result = \"\"\n        var c: char\n        while true:\n            c = getchar()\n            if c == ' ' or c == '\\n':\n                break\n            result &= c\n    #chmin,chmax\n    template `max=`(x, y) = x = max(x, y)\n    template `min=`(x, y) = x = min(x, y)\n    #bit演算\n    proc `%`*(x: int, y: int): int =\n        result = x mod y\n        if y > 0 and result < 0: result += y\n        if y < 0 and result > 0: result += y\n    proc `//`*(x: int, y: int): int{.inline.} =\n        result = x div y\n        if y > 0 and result * y > x: result -= 1\n        if y < 0 and result * y < x: result -= 1\n    proc `%=`(x: var int, y: int): void = x = x%y\n    proc `//=`(x: var int, y: int): void = x = x//y\n    proc `**`(x: int, y: int): int = x^y\n    proc `**=`(x: var int, y: int): void = x = x^y\n    proc `^`(x: int, y: int): int = x xor y\n    proc `|`(x: int, y: int): int = x or y\n    proc `&`(x: int, y: int): int = x and y\n    proc `>>`(x: int, y: int): int = x shr y\n    proc `<<`(x: int, y: int): int = x shl y\n    proc `~`(x: int): int = not x\n    proc `^=`(x: var int, y: int): void = x = x ^ y\n    proc `&=`(x: var int, y: int): void = x = x & y\n    proc `|=`(x: var int, y: int): void = x = x | y\n    proc `>>=`(x: var int, y: int): void = x = x >> y\n    proc `<<=`(x: var int, y: int): void = x = x << y\n    proc `[]`(x: int, n: int): bool = (x and (1 shl n)) != 0\n    #便利な変換\n    proc `!`(x: char, a = '0'): int = int(x)-int(a)\n    #定数\n    #[ include cplib/utils/constants ]#\n    when not declared CPLIB_UTILS_CONSTANTS:\n        const CPLIB_UTILS_CONSTANTS* = 1\n        const INF32*: int32 = 100100111.int32\n        const INF64*: int = int(3300300300300300491)\n    const INF = INF64\n    #converter\n\n    #range\n    iterator range(start: int, ends: int, step: int): int =\n        var i = start\n        if step < 0:\n            while i > ends:\n                yield i\n                i += step\n        elif step > 0:\n            while i < ends:\n                yield i\n                i += step\n    iterator range(ends: int): int = (for i in 0..<ends: yield i)\n    iterator range(start: int, ends: int): int = (for i in\n            start..<ends: yield i)\n\n    #joinが非stringでめちゃくちゃ遅いやつのパッチ\n    proc join*[T: not string](a: openArray[T], sep: string = \"\"): string = a.mapit($it).join(sep)\n"
ImportExpand "cplib/collections/segtree.nim" <=== "when not declared CPLIB_COLLECTIONS_SEGTREE:\n    const CPLIB_COLLECTIONS_SEGTREE* = 1\n    import algorithm\n    import strutils\n    import sequtils\n    type SegmentTree*[T] = ref object\n        default: T\n        merge: proc(x: T, y: T): T\n        arr*: seq[T]\n        lastnode: int\n        length: int\n    proc initSegmentTree*[T](v: seq[T], merge: proc(x: T, y: T): T, default: T): SegmentTree[T] =\n        ## セグメントツリーを生成します。\n        ## vに元となるリスト、mergeに二つの区間をマージする関数、デフォルトに単位元を与えてください。\n        var lastnode = 1\n        while lastnode < len(v):\n            lastnode*=2\n        var arr = newSeq[T](2*lastnode)\n        arr.fill(default)\n        var self = SegmentTree[T](default: default, merge: merge, arr: arr, lastnode: lastnode, length: len(v))\n        #1-indexedで作成する\n        for i in 0..<len(v):\n            self.arr[self.lastnode+i] = v[i]\n        for i in countdown(lastnode-1, 1):\n            self.arr[i] = self.merge(self.arr[2*i], self.arr[2*i+1])\n        return self\n    proc initSegmentTree*[T](n: int, merge: proc(x: T, y: T): T, default: T): SegmentTree[T] =\n        ## セグメントツリーを生成します。\n        ## nにサイズ、mergeに二つの区間をマージする関数、デフォルトに単位元を与えてください。（全て単位元で構築されます）\n        initSegmentTree(newSeqWith(n, default), merge, default)\n\n    proc update*[T](self: SegmentTree[T], x: Natural, val: T) =\n        ## xの要素をvalに変更します。\n        assert x < self.length\n        var x = x\n        x += self.lastnode\n        self.arr[x] = val\n        while x > 1:\n            x = x shr 1\n            self.arr[x] = self.merge(self.arr[2*x], self.arr[2*x+1])\n    proc get*[T](self: SegmentTree[T], q_left: Natural, q_right: Natural): T =\n        ## 半解区間[q_left,q_right)についての演算結果を返します。\n        assert q_left <= q_right and 0 <= q_left and q_right <= self.length\n        var q_left = q_left\n        var q_right = q_right\n        q_left += self.lastnode\n        q_right += self.lastnode\n        var (lres, rres) = (self.default, self.default)\n        while q_left < q_right:\n            if (q_left and 1) > 0:\n                lres = self.merge(lres, self.arr[q_left])\n                q_left += 1\n            if (q_right and 1) > 0:\n                q_right -= 1\n                rres = self.merge(self.arr[q_right], rres)\n            q_left = q_left shr 1\n            q_right = q_right shr 1\n        return self.merge(lres, rres)\n    proc get*[T](self: SegmentTree[T], segment: HSlice[int, int]): T =\n        assert segment.a <= segment.b + 1 and 0 <= segment.a and segment.b+1 <= self.length\n        return self.get(segment.a, segment.b+1)\n    proc `[]`*[T](self: SegmentTree[T], segment: HSlice[int, int]): T = self.get(segment)\n    proc `[]`*[T](self: SegmentTree[T], index: Natural): T =\n        assert index < self.length\n        return self.arr[index+self.lastnode]\n    proc `[]=`*[T](self: SegmentTree[T], index: Natural, val: T) =\n        assert index < self.length\n        self.update(index, val)\n    proc get_all*[T](self: SegmentTree[T]): T =\n        ## [0,len(self))区間の演算結果をO(1)で返す\n        return self.arr[1]\n    proc len*[T](self: SegmentTree[T]): int =\n        return self.length\n    proc `$`*[T](self: SegmentTree[T]): string =\n        var s = self.arr.len div 2\n        return self.arr[s..<s+self.len].join(\" \")\n    template newSegWith*(V, merge, default: untyped): untyped =\n        initSegmentTree[typeof(default)](V, proc (l{.inject.}, r{.inject.}: typeof(default)): typeof(default) = merge, default)\n    proc max_right*[T](self: SegmentTree[T], l: int, f: proc(l: T): bool): int =\n        assert 0 <= l and l <= self.len\n        assert f(self.default)\n        if l == self.len: return self.len\n        var l = l\n        l += self.lastnode\n        var sm = self.default\n        while true:\n            while l mod 2 == 0: l = (l shr 1)\n            if not f(self.merge(sm, self.arr[l])):\n                while l < self.lastnode:\n                    l *= 2\n                    if f(self.merge(sm, self.arr[l])):\n                        sm = self.merge(sm, self.arr[l])\n                        l += 1\n                return l - self.lastnode\n            sm = self.merge(sm, self.arr[l])\n            l += 1\n            if (l and -l) == l: break\n        return self.len\n    proc min_left*[T](self: SegmentTree[T], r: int, f: proc(l: T): bool): int =\n        assert 0 <= r and r <= self.len\n        assert f(self.default)\n        if r == 0: return 0\n        var r = r\n        r += self.lastnode\n        var sm = self.default\n        while true:\n            r -= 1\n            while (r > 1 and r mod 2 != 0): r = (r shr 1)\n            if not f(self.merge(self.arr[r], sm)):\n                while r < self.lastnode:\n                    r = 2 * r + 1\n                    if f(self.merge(self.arr[r], sm)):\n                        sm = self.merge(self.arr[r], sm)\n                        r -= 1\n                return r + 1 - self.lastnode\n            if (r and -r) == r: break\n        return 0\n"
ImportExpand "cplib/utils/binary_search.nim" <=== "when not declared CPLIB_UTILS_BINARY_SEARCH:\n    const CPLIB_UTILS_BINARY_SEARCH* = 1\n    proc meguru_bisect*(ok, ng: int, is_ok: proc(x: int): bool): int =\n        var\n            ok = ok\n            ng = ng\n        while abs(ok - ng) > 1:\n            var mid = (ok + ng) div 2\n            if is_ok(mid): ok = mid\n            else: ng = mid\n        return ok\n\n    proc meguru_bisect*(ok, ng: SomeFloat, is_ok: proc(x: SomeFloat): bool, eps: SomeFloat = 1e-10): SomeFloat =\n        var\n            ok = ok\n            ng = ng\n        while abs(ok - ng) > eps and abs(ok - ng) / max(ok, ng) > eps:\n            var mid = (ok + ng) / 2\n            if is_ok(mid): ok = mid\n            else: ng = mid\n        return ok\n"

var Q,Y = ii()
var S = newSeqWith(Q,si())
proc solve(x:int):int=
    var A : seq[int]
    for i in range(Q):
        if S[i] == "min":
            A.add(min(A.pop(),A.pop()))
        elif S[i] == "max":
            A.add(max(A.pop(),A.pop()))
        elif S[i] == "+":
            A.add((A.pop()+A.pop()))
        elif S[i] == "X":
            A.add(x)
        else:
            A.add(S[i].parseInt)
    return A[0]
proc isok(arg:int):bool=
    
    return solve(arg) >= Y

var tmp = meguru_bisect(10**14,-1,isok)
if solve(tmp) == Y:
    echo tmp
else:
    echo "-1"