# include <bits/stdc++.h>
# define pb push_back
//# define int long long
# define db long double
using namespace std;

const int N = 500005;

int n, q, cnt = 0, root[N];

struct node{
	int l, r;
} tree[N << 2];

void Build(int &rt, int st, int end){
	rt = ++cnt;
	if (st == end) return ;
	int mid = (st + end) >> 1;
	Build(tree[rt].l, st, mid);
	Build(tree[rt].r, mid+1, end);
}

int Update(int u, int v, int st, int end, int l, int r){
	if (!u) return 0;
	if (l <= st && end <= r) return u;
	int rt = ++cnt, mid = (st + end) >> 1;
	tree[rt] = tree[v];
	if (l <= mid) tree[rt].l = Update(tree[u].l, tree[v].l, st, mid, l, r);
	if (r > mid) tree[rt].r = Update(tree[u].r, tree[v].r, mid+1, end, l, r);
	if (tree[rt].l == 0 && tree[rt].r == 0) return 0;
	return rt;
}

int Query(int rt, int st, int end, int l, int r){
	if (!rt) return 0;
	if (l <= st && end <= r) return 1;
	int mid = (st + end) >> 1, ret = 0;
	if (l <= mid) ret |= Query(tree[rt].l, st, mid, l, r);
	if (r > mid) ret |= Query(tree[rt].r, mid+1, end, l, r);
	return ret;
}

int main(){
	scanf("%d%d", &n, &q);
	Build(root[0], 1, n);
	for (int i = 1;i <= q;i++){
		int opt, l, r, x; scanf("%d%d%d", &opt, &l, &r);
		if (opt == 1){
			scanf("%d", &x);
			root[x+1] = Update(root[x], root[x+1], 1, n, l, r);
		}
		else{
			int L = 0, R = i+1;
			while (L < R-1){
				int mid = (L + R) >> 1;
				if (Query(root[mid], 1, n, l, r)) L = mid;
				else R = mid;
			}
			printf("%d\n", L);
		}
	}
	return 0;
}