codeforces960F. Pathwalks_树状数组

F. Pathwalks

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

You are given a directed graph with n nodes and m edges, with all edges having a certain weight.

There might be multiple edges and self loops, and the graph can also be disconnected.

You need to choose a path (possibly passing through same vertices multiple times) in the graph such that the weights of the edges are in strictly increasing order, and these edges come in the order of input. Among all such paths, you need to find the the path that has the maximum possible number of edges, and report this value.

Please note that the edges picked don't have to be consecutive in the input.

Input

The first line contains two integers n and m (1 ≤ n ≤ 100000,1 ≤ m ≤ 100000) — the number of vertices and edges in the graph, respectively.

m lines follows.

The i-th of these lines contains three space separated integers a_i, b_i and w_i (1 ≤ a_i, b_i ≤ n, 0 ≤ w_i ≤ 100000), denoting an edge from vertex a_i to vertex b_i having weight w_i

Output

Print one integer in a single line — the maximum number of edges in the path.

Examples

Input

Copy

3 3
3 1 3
1 2 1
2 3 2

Output

Copy

2

Input

Copy

5 5
1 3 2
3 2 3
3 4 5
5 4 0
4 5 8

Output

Copy

3

Note

The answer for the first sample input is 2: . Note that you cannot traverse because edge appears earlier in the input than the other two edges and hence cannot be picked/traversed after either of the other two edges.

In the second sample, it's optimal to pick 1-st, 3-rd and 5-th edges to get the optimal answer: .

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define all(x) (x).begin(),x.end()
ll rd(){
    ll x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
#define rep(i,a,n) for(int i=a;i<n;i++)
#define se second
const int N=100100;
map<int,int> c[N];
int query(int u,int w){
    int s=0;
    for(;w;w-=w&-w){
        auto it=c[u].find(w);
        if(it!=c[u].end())s=max(s,it->se);
    }
    return s;
}

void modify(int u,int w,int s){
    for(;w<=100001;w+=w&-w)c[u][w]=max(c[u][w],s);
}

int main(){
    //freopen("in.txt","r",stdin);
    int n=rd(),m=rd();
    rep(i,0,m){
        int u=rd(),v=rd(),w=rd();
        w++;
        modify(v,w,query(u,w-1)+1);
    }
    int ret=0;
    rep(i,1,n+1)ret=max(ret,query(i,100001));
    cout<<ret<<endl;
}