# include <bits/stdc++.h>
using namespace std;
int n,m;
struct operation { int opt,l,r,x;} op[500010];
struct Persistent_SegmentTree {
    int l,r,cnt,ro[500010];
    struct node { int son[2];} f[20000010];

    int get_newnode_() { cnt++, f[cnt].son[0]=f[cnt].son[1]=0; return cnt;}
    int build_(int l,int r) {
        int x=get_newnode_();
        if (l==r) return x;
        int mid=(l+r)>>1;
        f[x].son[0]=build_(l,mid), f[x].son[1]=build_(mid+1,r);
        return x;
    }
    int copy_(int x,int y,int l,int r,int lpos,int rpos) {
        if (lpos<=l&&r<=rpos) return y;
        if (!y) return 0;
        int k=get_newnode_(); f[k].son[0]=f[x].son[0], f[k].son[1]=f[x].son[1];
        int mid=(l+r)>>1;
        if (lpos<=mid) f[k].son[0]=copy_(f[k].son[0],f[y].son[0],l,mid,lpos,rpos);
        if (mid<rpos) f[k].son[1]=copy_(f[k].son[1],f[y].son[1],mid+1,r,lpos,rpos);
        return k;
    }
    bool check_(int x,int l,int r,int lpos,int rpos) {
        if (!x) return false;
        if (lpos<=l&&r<=rpos) return true;
        bool ans=0;
        int mid=(l+r)>>1;
        if (lpos<=mid) ans|=check_(f[x].son[0],l,mid,lpos,rpos);
        if (mid<rpos) ans|=check_(f[x].son[1],mid+1,r,lpos,rpos);
        return ans;
    }
    
    void init_(int _l,int _r) { l=_l, r=_r, cnt=0, memset(ro,0,sizeof(ro));}
    void build_(int a) { ro[a]=build_(l,r);}
    void copy_(int a,int b,int l,int r) { ro[a]=copy_(ro[a],ro[b],this -> l,this -> r,l,r);}
    bool check_(int a,int l,int r) { return check_(ro[a],this -> l,this -> r,l,r);}
} pst;
int main() {
    // freopen("in.in","r",stdin);
    // freopen("out.out","w",stdout);

    scanf("%d%d",&n,&m);
    for (int i=1;i<=m;i++) {
        scanf("%d",&op[i].opt);
        if (op[i].opt==1) scanf("%d%d%d",&op[i].l,&op[i].r,&op[i].x);
        else scanf("%d%d",&op[i].l,&op[i].r);
    }

    vector<int> ans;
    pst.init_(1,n), pst.build_(0);
    for (int i=1;i<=m;i++) {
        if (op[i].opt==1) pst.copy_(op[i].x+1,op[i].x,op[i].l,op[i].r);
        else {
            int l=1,r=m+1;
            while (l<r) {
                int mid=(l+r)>>1;
                if (pst.check_(mid,op[i].l,op[i].r)) l=mid+1;
                else r=mid;
            }
            ans.push_back(l-1);
        }
    }

    for (auto o : ans) printf("%d\n",o);

    fprintf(stderr,"%lf\n",clock()/1.0/CLOCKS_PER_SEC);
    return 0;
}