import sys

# sys.setrecursionlimit(200005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
# md = 998244353

class LazySegTree:
    def __init__(self, op, e, mapping, composition, _id, v):
        self._op = op
        self._e = e
        self._mapping = mapping
        self._composition = composition
        self._id = _id

        if isinstance(v, int):
            v = [e]*v

        self._n = len(v)
        self._log = (self._n-1).bit_length()
        self._size = 1 << self._log
        self._d = [self._e]*(2*self._size)
        self._lz = [self._id]*self._size
        for i in range(self._n):
            self._d[self._size+i] = v[i]
        for i in range(self._size-1, 0, -1):
            self._update(i)

    def set(self, p, x):
        p += self._size
        for i in range(self._log, 0, -1):
            self._push(p >> i)
        self._d[p] = x
        for i in range(1, self._log+1):
            self._update(p >> i)

    def get(self, p):
        p += self._size
        for i in range(self._log, 0, -1):
            self._push(p >> i)
        return self._d[p]

    def prod(self, left, right):
        if left == right:
            return self._e

        left += self._size
        right += self._size

        for i in range(self._log, 0, -1):
            if ((left >> i) << i) != left:
                self._push(left >> i)
            if ((right >> i) << i) != right:
                self._push(right >> i)

        sml = self._e
        smr = self._e
        while left < right:
            if left & 1:
                sml = self._op(sml, self._d[left])
                left += 1
            if right & 1:
                right -= 1
                smr = self._op(self._d[right], smr)
            left >>= 1
            right >>= 1

        return self._op(sml, smr)

    def all_prod(self):
        return self._d[1]

    def apply(self, left, right, f):
        if right is None:
            p = left
            p += self._size
            for i in range(self._log, 0, -1):
                self._push(p >> i)
            self._d[p] = self._mapping(f, self._d[p])
            for i in range(1, self._log+1):
                self._update(p >> i)
        else:
            if left == right:
                return

            left += self._size
            right += self._size

            for i in range(self._log, 0, -1):
                if ((left >> i) << i) != left:
                    self._push(left >> i)
                if ((right >> i) << i) != right:
                    self._push((right-1) >> i)

            l2 = left
            r2 = right
            while left < right:
                if left & 1:
                    self._all_apply(left, f)
                    left += 1
                if right & 1:
                    right -= 1
                    self._all_apply(right, f)
                left >>= 1
                right >>= 1
            left = l2
            right = r2

            for i in range(1, self._log+1):
                if ((left >> i) << i) != left:
                    self._update(left >> i)
                if ((right >> i) << i) != right:
                    self._update((right-1) >> i)

    def max_right(self, left, g):
        if left == self._n:
            return self._n

        left += self._size
        for i in range(self._log, 0, -1):
            self._push(left >> i)

        sm = self._e
        first = True
        while first or (left & -left) != left:
            first = False
            while left%2 == 0:
                left >>= 1
            if not g(self._op(sm, self._d[left])):
                while left < self._size:
                    self._push(left)
                    left *= 2
                    if g(self._op(sm, self._d[left])):
                        sm = self._op(sm, self._d[left])
                        left += 1
                return left-self._size
            sm = self._op(sm, self._d[left])
            left += 1

        return self._n

    def min_left(self, right, g):
        if right == 0:
            return 0

        right += self._size
        for i in range(self._log, 0, -1):
            self._push((right-1) >> i)

        sm = self._e
        first = True
        while first or (right & -right) != right:
            first = False
            right -= 1
            while right > 1 and right%2:
                right >>= 1
            if not g(self._op(self._d[right], sm)):
                while right < self._size:
                    self._push(right)
                    right = 2*right+1
                    if g(self._op(self._d[right], sm)):
                        sm = self._op(self._d[right], sm)
                        right -= 1
                return right+1-self._size
            sm = self._op(self._d[right], sm)

        return 0

    def _update(self, k):
        self._d[k] = self._op(self._d[2*k], self._d[2*k+1])

    def _all_apply(self, k, f):
        self._d[k] = self._mapping(f, self._d[k])
        if k < self._size:
            self._lz[k] = self._composition(f, self._lz[k])

    def _push(self, k):
        self._all_apply(2*k, self._lz[k])
        self._all_apply(2*k+1, self._lz[k])
        self._lz[k] = self._id

def op(x, y):
    h1, s1 = divmod(x, 1 << 20)
    h2, s2 = divmod(y, 1 << 20)
    h = (h1*power[s2]%md+h2)%md
    s = s1+s2
    return h << 20 | s

# treeの単位元
e = 0

# lazy(f)からtree(x)への操作
def mapping(f, x):
    if f == 0: return x
    h, s = divmod(x, 1 << 20)
    h += ones[s]*f
    h %= md
    return h << 20 | s

# lazyの下への分解
def composition(f, g):
    return f+g

# lazyの単位元
_id = 0

from random import randrange

md = 2147483587
base = randrange(20000000, 20001000)
power = [1]
ones = [0]
for _ in range(10**6):
    power.append(power[-1]*base%md)
    ones.append((ones[-1]*base+1)%md)

n, Q = LI()
seg = LazySegTree(op, e, mapping, composition, _id, [1]*n)
h2q={0:0}
h=0
for q in range(1,Q+1):
    t,*data=SI().split()
    if t=="!":
        l,r,k=map(int,data)
        seg.apply(l,r,k)
        h=seg.all_prod()>>20
        if h not in h2q:h2q[h]=q
    else:
        print(h2q[h])