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

typedef long long ll;
typedef vector< int > vi;
typedef vector< vi > vvi;
typedef vector< ll > vl;
typedef vector< vl > vvl;
typedef pair< int, int > pii;
typedef vector< pii > vp;
typedef vector< double > vd;
typedef vector< vd > vvd;
typedef vector< string > vs;

template< class T1, class T2 >
int upmin( T1 &x, T2 v ){
  if( x > v ){
    x = v;
    return 1;
  }
  return 0;
}

template< class T1, class T2 >
int upmax( T1 &x, T2 v ){
  if( x < v ){
    x = v;
    return 1;
  }
  return 0;
}

const int INF = 0x3f3f3f3f;

int N, Q;

void init(){
  cin >> N >> Q;
}

const int HASH_T = 3;
const int MAXN = ( int ) 1e6;

int base[ HASH_T ] = { 10003, 10007, 10009 };
int base_psum[ HASH_T ][ MAXN + 1 ];
int mod[ HASH_T ] = { ( int ) 1e9 + 7, ( int ) 1e9 + 9, 1114111 };

void preprocess(){
  for( int t = 0; t < HASH_T; ++t ){
    int cb = 1;
    for( int i = 0; i < N; ++i ){
      base_psum[ t ][ i + 1 ] = ( base_psum[ t ][ i ] + cb ) % mod[ t ];
      cb = 1LL * cb * base[ t ] % mod[ t ];
    }
  }
}

void solve(){
  map< vi, int > earliest;
  vi chv( HASH_T ); // current hash values
  earliest[ chv ] = 0;
  for( int i = 0; i < Q; ++i ){
    string op; cin >> op;
    if( op == "!" ){
      int L, R, K; cin >> L >> R >> K;
      for( int t = 0; t < HASH_T; ++t ){
        int diff = ( base_psum[ t ][ R ] - base_psum[ t ][ L ] ) % mod[ t ];
        diff = 1LL * diff * K % mod[ t ];
        ( chv[ t ] += diff ) %= mod[ t ];
        if( chv[ t ] < 0 )
          chv[ t ] += mod[ t ];
      }
      if( not earliest.count( chv ) )
        earliest[ chv ] = i + 1;
    } else{
      cout << earliest[ chv ] << endl;
    }
  }
}

signed main(){
  ios::sync_with_stdio( 0 );
  init();
  preprocess();
  solve();
  return 0;
}