#include <bits/stdc++.h>
using namespace std;

const int mod = 1e9 + 7;

int add(int x, int y) {
    return (x += y) >= mod ? x - mod : x;
}

int sub(int x, int y) {
    return add(x, mod - y);
}

int mul(int x, int y) {
    return 1LL * x * y % mod;
}

int main() {
    int n, q;
    cin >> n >> q;

    const int mod = 1e9 + 7;
    srand(time(NULL));
    int base1 = rand() + 2;
    int base2 = rand() + 2;
    int base3 = rand() + 2;

    vector<int> ws1(n + 1);
    vector<int> ws2(n + 1);
    vector<int> ws3(n + 1);
    int p1 = 1;
    int p2 = 1;
    int p3 = 1;
    for (int i = 1; i <= n; i++) {
        ws1[i] = add(ws1[i - 1], p1);
        ws2[i] = add(ws2[i - 1], p2); 
        ws3[i] = add(ws3[i - 1], p3);
        p1 = mul(p1, base1);
        p2 = mul(p2, base2);
        p3 = mul(p3, base3);
    }

    int rh1 = 0;
    int rh2 = 0;
    int rh3 = 0;
    map<tuple<int, int, int>, int> mp;
    mp[make_tuple(0, 0, 0)] = 0;
    for (int i = 1; i <= q; i++) {
        char c;
        scanf(" %c", &c);

        if (c == '!') {
            int l, r, v;
            scanf("%d %d %d", &l, &r, &v);
            v %= mod;
            if (v < 0) {
                v += mod;
            }
            rh1 = add(rh1, mul(v, sub(ws1[r], ws1[l])));
            rh2 = add(rh2, mul(v, sub(ws2[r], ws2[l])));
            rh3 = add(rh3, mul(v, sub(ws3[r], ws3[l])));
            tuple<int, int, int> curr(rh1, rh2, rh3);
            if (mp.count(curr) == 0) {
                mp[curr] = i;
            }
        } else {
            tuple<int, int, int> curr(rh1, rh2, rh3);
            printf("%d\n", mp[curr]);
        }
    }
}