#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#define endl '\n'
using namespace std;
const int N=5e5+10,B=1510;
int pos[N],fa[B],ans,a[N],siz[B];
int L[N],R[N],fat[B],val[B],num;
namespace nqio{const unsigned R=4e5,W=4e5;char*a,*b,i[R],o[W],*c=o,*d=o+W,h[40],*p=h,y;bool s;struct q{void r(char&x){x=a==b&&(b=(a=i)+fread(i,1,R,stdin),a==b)?-1:*a++;}void f() {fwrite(o,1,c-o,stdout);c=o;}~q(){f();}void w(char x) {*c=x;if(++c==d)f();}q&operator>>(char&x){do r(x);while(x<=32);return*this;}q&operator>>(char*x){do r(*x);while(*x<=32);while(*x>32)r(*++x);*x=0;return*this;}template<typename t>q&operator>>(t&x) {for(r(y),s=0;!isdigit(y);r(y))s|=y==45;if(s)for(x=0;isdigit(y);r(y))x=x*10- (y^48);else for(x=0;isdigit(y);r(y))x=x*10+ (y^48);return*this;}q&operator<<(char x) {w(x);return*this;}q&operator<<(char*x) {while(*x)w(*x++);return*this;}q&operator<<(const char*x) {while(*x)w(*x++);return*this;}template<typename t>q&operator<<(t x) {if(!x)w(48);else if(x<0)for(w(45);x;x/=10)*p++=48|-(x%10);else for(;x;x/=10)*p++=48|x%10;while(p!=h)w(*--p);return*this;}}qio;}using nqio::qio;
struct node{
	int opt,l,r,k,ans;
}q[N];
int find(int x){
	if (fa[x]!=x) fa[x]=find(fa[x]);
	return fa[x];
}
void merge(int x, int y){
	int fx=find(x),fy=find(y);
	if (siz[fx]<siz[fy]){
		fa[fx]=fy,siz[fy]+=siz[fx];
	}else fa[fy]=fx,siz[fx]+=siz[fy];
	return;
}
void pushdown(int id){
	for (int i=L[id];i<=R[id];i++){
		a[i]=val[find(fat[i-L[id]])];
		fat[i-L[id]]=0;
	}for (int i=1;i<=num;i++){
		pos[val[i]]=0;fa[i]=0;val[i]=0;siz[i]=0;
	}ans=num=0;return;
}
void build(int id){
	int cnt=0;
	for (int i=L[id];i<=R[id];i++){
		if (!pos[a[i]]){
			fat[i-L[id]]=++cnt;fa[cnt]=cnt;
			pos[a[i]]=cnt;val[cnt]=a[i];siz[cnt]=1;
		}else fat[i-L[id]]=pos[a[i]];
		ans=max(ans,a[i]);
	}num=cnt;return;
}
void modify(int k){
	if (!pos[k]) return;
	int x=pos[k];
	if (!pos[k+1]){
		pos[k]=0;pos[k+1]=x;val[x]=k+1;
	}else{
		int fx=find(x),fy=find(pos[k+1]);
		pos[k]=0;val[x]=k+1;pos[k+1]=0;
		if (siz[fx]<siz[fy]){
			fa[fx]=fy,siz[fy]+=siz[fx];
		}else{
			fa[fy]=fx,siz[fx]+=siz[fy];
			pos[k+1]=fx;
		}
	}ans=max(ans,k+1);return;
}
bool check(int l, int r, int id){
	if (r>=L[id]&&l<=L[id]) return 1;
	if (r>=R[id]&&l<=R[id]) return 1;
	if (L[id]<=l&&r<=R[id]) return 1;
	return 0;
}
int main(){
	ios::sync_with_stdio(0);
	int n,m;qio>>n>>m;int b=0,t=900;
	for (int i=1;i<=n;i++){
		L[i]=R[i-1]+1;R[i]=min(i*t,n);
		b++;if (R[i]==n) break;
	}for (int i=1;i<=m;i++){
		int opt,l,r,k=0;qio>>opt>>l>>r;
		if (opt==1) qio>>k;
		q[i]={opt,l,r,k,0};
	}for (int i=1;i<=b;i++){
		build(i);
		for (int j=1;j<=m;j++){
			if (q[j].l<=L[i]&&q[j].r>=R[i]){
				if (q[j].opt==1) modify(q[j].k);
				else q[j].ans=max(q[j].ans,ans);
			}else if (check(q[j].l,q[j].r,i)){
				pushdown(i);
				int l=max(L[i],q[j].l),r=min(R[i],q[j].r);
				for (int k=l;k<=r;k++){
					if (q[j].opt==1) {if (a[k]==q[j].k) a[k]++;}
					else q[j].ans=max(q[j].ans,a[k]);
				}build(i);
			}
		}pushdown(i);
	}for (int i=1;i<=m;i++){
		if (q[i].opt==2) qio<<q[i].ans<<endl;
	}return 0;
}