from collections import defaultdict
from random import randint


pool = defaultdict(lambda: randint(1, (1 << 61) - 1))
curHash = 0
history = {0: 0}

n, q = map(int, input().split())
for i in range(q):
    op, *args = input().split()
    if op == "?":
        print(history.get(curHash, -1))
    else:
        left, rigth, add = map(int, args)
        curHash += (pool[rigth] - pool[left]) * add
        history.setdefault(curHash, i + 1)