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

#define _p(...) (void)printf(__VA_ARGS__)
#define forr(x,arr) for(auto&& x:arr)
#define _overload3(_1,_2,_3,name,...) name
#define _rep2(i,n) _rep3(i,0,n)
#define _rep3(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload3(__VA_ARGS__,_rep3,_rep2,)(__VA_ARGS__)
#define _rrep2(i,n) _rrep3(i,0,n)
#define _rrep3(i,a,b) for(int i=int(b)-1;i>=int(a);i--)
#define rrep(...) _overload3(__VA_ARGS__,_rrep3,_rrep2,)(__VA_ARGS__)
#define all(x) (x).begin(), (x).end()
#define bit(n) (1LL<<(n))
#define sz(x) ((int)(x).size())
#define fst first
#define snd second
using ll=long long;using pii=pair<int,int>;
using vb=vector<bool>;using vs=vector<string>;
using vi=vector<int>;using vvi=vector<vi>;using vvvi=vector<vvi>;
using vl=vector<ll>;using vvl=vector<vl>;using vvvl=vector<vvl>;
using vd=vector<double>;using vvd=vector<vd>;using vvvd=vector<vvd>;
using vpii=vector<pii>;using vvpii=vector<vpii>;using vvvpii=vector<vvpii>;
template<typename T>T read(){T t;cin>>t;return t;}
template<class T,class U>ostream&operator<<(ostream&o,const pair<T,U>&p){o<<'('<<p.fst<<", "<<p.snd<<')';return o;}

struct RollingHash64 {
  const int base = 1e9+7;
  const int N;
  vector<long long> P, H;

  /**
   * O(N)
   */
  RollingHash64(const vi & S) : N(S.size()), P(N+1, 1), H(N+1, 0) {
    for (int i = 0; i < N; i++) {
      int c = S[i];
      H[i+1] = H[i] * base + c;
      P[i+1] = P[i] * base;
    }
  }

  /**
   * S全体のハッシュ値を返す
   * O(1)
   */
  long long hash() const {
    return hash(0, N);
  }

  /**
   * S の [l, r) のハッシュ値を返す
   * O(1)
   */
  long long hash(int l, int r) const {
    return H[r] - H[l] * P[r - l];
  }

  /**
   * S の [l1, r1) と [l2, r2) のハッシュ値が等しいかを返す
   * O(1)
   */
  bool equals(int l1, int r1, int l2, int r2) const {
    if (l1 < 0 || l2 < 0) return false;
    if (r1 > N || r2 > N) return false;
    if (r1 - l1 != r2 - l2) return false;
    return hash(l1, r1) == hash(l2, r2);
  }

  /**
   * S の p1 からの len 文字と p2 からの len 文字が等しいかを返す
   * O(1)
   */
  bool equals(int p1, int p2, int len) const {
    return equals(p1, p1 + len, p2, p2 + len);
  }

  /**
   * S の pos 以降と other が等しいかを返す
   * O(1)
   */
  bool equals(int pos, const RollingHash64 &other) const {
    int r = pos + other.N;
    if (r >= N) return false;

    return hash(pos, r) == hash(0, other.N);
  }
};

void Main() {
  int n = read<int>();
  int Q = read<int>();

  vi A(n+1);
  RollingHash64 rh(A);

  map<ll, int> first;

  ll current = rh.hash();
  first[current] = 0;

  rep(q, Q) {
    char t = read<char>();
    if (t == '!') {
      int l = read<int>();
      int r = read<int>();
      int k = read<int>();

      A[l] += k;
      A[r] -= k;

      ll sl = rh.P[l] * k;
      ll sr = rh.P[r] * -k;
      current += sl;
      current += sr;
      if (first.count(current) == 0) {
        first[current] = q + 1;
      }
    }
    else {
      cout << first[current] << endl;
    }
    //cout << q << " : "; rep(ii,sz(A)) cout << ' ' << A[ii]; cout << endl;
  }
}
int main() { cin.tie(nullptr); ios::sync_with_stdio(false); Main(); return 0; }