#include <bits/stdc++.h>
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define FORR(i,a,b) for (int i=(a);i>=(b);i--)
#define pb push_back
#define pcnt __builtin_popcount
#define show(x) cout<<#x<<" = "<<x<<endl;
#define maxs(x,y) x = max(x,y)
#define mins(x,y) x = min(x,y)
#define fi first
#define se second
#define rng(a) a.begin(),a.end()
#define each(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define sz(x) (int)(x).size()
#define mp make_pair

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<pii> vpii;
typedef set<int> si;
typedef pair<ll,ll> pll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<pll> vpll;
typedef set<ll> sl;
typedef __int128_t lll;
typedef pair<lll,lll> plll;
typedef vector<lll> vlll;
template<typename T>string join(vector<T>&v)
{stringstream s;FOR(i,0,sz(v))s<<' '<<v[i];return s.str().substr(1);}
ll gcd(ll a,ll b){if(a>b)swap(a,b);for(;a>0;b%=a,swap(a,b));return b;}
int modpow(ll a,ll n,int m){if(a==0)return a;ll p=1;for(;n>0;n/=2,a=a*a%m)if(n&1)p=p*a%m;return(int)p;}
void dout(double d){printf("%.12f\n",d);}

const int iinf = 1e9;
const ll linf = 1e18;
const double pi = acos(-1);
const double eps = 1e-10;
const ll d = 19999;
int n, q, l, r, k;
char c;
ll p[1000001][2], s[1000001][2], mod[2] = {1000000007, 1000000021};
map<pll, int> m;
main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  p[0][0] = 1;
  p[0][1] = 1;
  FOR(j, 0, 2)FOR(i, 1, 1000001){
    p[i][j] = p[i-1][j] * d % mod[j];
    s[i][j] = (s[i-1][j] * d + 1) % mod[j];
  }
  cin >> n >> q;
  ll h[2] = {0, 0};
  pll b;
  b = mp(0,0);
  m[b] = 0;
  FOR(i, 1, q+1){
    cin >> c ;
    if(c == '!'){
      cin >> l >> r >> k;
      FOR(j, 0, 2) h[j] = (h[j] + p[l][j] * s[r-l][j] % mod[j] * ((k+mod[j])%mod[j])) % mod[j];
      b = mp(h[0], h[1]);
      if(m.find(b) == m.end()) m[b] = i;
    }else{
      b = mp(h[0], h[1]);
      cout << m[b] << "\n";
    }
  }
  return 0;
}