#include <iostream>
#include <cstdio>
#include <chrono>
#include <map>
#include <random>

using namespace std;

typedef unsigned long long ULL;

const int N = 1000010;
const ULL P = 1000000007ULL;

ULL r1[N], r2[N], pre1[N], pre2[N];
ULL h1, h2;
int n, q;
map<ULL, int> mp;

int main() {
    mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
    scanf("%d%d", &n, &q);
    for (int i = 0; i < n; ++i) {
        r1[i] = rng();
        r2[i] = rng();
    }
    for (int i = 0; i < n; ++i) {
        pre1[i + 1] = pre1[i] + r1[i];
        pre2[i + 1] = pre2[i] + r2[i];
    }

    mp[0] = 0;
    for (int i = 1; i <= q; ++i) {
        char type;
        scanf(" %c", &type);
        if (type == '!') {
            int l, r, k;
            scanf("%d%d%d", &l, &r, &k);
            h1 += (ULL) k * (pre1[r] - pre1[l]);
            h2 += (ULL) k * (pre2[r] - pre2[l]);
            ULL key = h1 * P + h2;
            if (!mp.count(key)) mp[key] = i;
        } else {
            printf("%d\n", mp[h1 * P + h2]);
        }
    }

    return 0;
}