差分约束

#include<bits/stdc++.h>
using namespace std;
//input by bxd
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define repp(i,a,b) for(int i=(a);i>=(b);--i)
#define RI(n) scanf("%d",&(n))
#define RII(n,m) scanf("%d%d",&n,&m)
#define RIII(n,m,k) scanf("%d%d%d",&n,&m,&k)
#define RS(s) scanf("%s",s);
#define ll long long
#define pb push_back
#define REP(i,N)  for(int i=0;i<(N);i++)
#define CLR(A,v)  memset(A,v,sizeof A)
#define inf 0x3f3f3f3f
//////////////////////////////////////
const int N = 200000+6;

int pos=0;
struct node
{
    int nex,to,v;
}edge[N];

int head[N];
void add(int a,int b,int v)
{
    edge[++pos].nex=head[a];
    head[a]=pos;
    edge[pos].to=b;
    edge[pos].v=v;
}

int dis[N],vis[N];
int L,R;
void spaf(int s)
{
    rep(i,L,R)
    dis[i]=-inf;
    dis[s]=0;
    queue<int>q;
    q.push(s);
    vis[s]=1;
    while(!q.empty())
    {
        int u=q.front();q.pop();
        vis[u]=0;
        for(int i=head[u];i;i=edge[i].nex)
        {
            int v=edge[i].to;
            if(dis[v]<dis[u]+edge[i].v)
            {
                dis[v]=dis[u]+edge[i].v;
                if(!vis[v])
                {
                    vis[v]=1;
                    q.push(v);
                }
            }
        }
    }
}
int main()
{
    int n;
    while(~RI(n))
    {
        pos=0;
        CLR(head,0);
        CLR(vis,0);
        L=inf;
        R=0;
        rep(i,1,n)
        {
            int a,b,c;
            RIII(a,b,c);a--;
            add(a,b,c);
            L=min(a,L);
            R=max(R,b);
        }
        rep(i,L,R-1)
        add(i,i+1,0),add(i+1,i,-1);
        spaf(L);
        cout<<dis[R]<<endl;
    }
    return 0;
}