树状数组实现单点修改+区间查询最小值，因为不能处理 0 边界所以所有 $l,r$ 全部 $+2$

#include<bits/stdc++.h>
#define ll long long
using namespace std;
mt19937 myrand(time(0));
inline ll read(){
	ll x=0,w=1;
	char ch=0;
	while(ch<'0'||ch>'9'){
		if(ch=='-')w=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9'){
		x=(x<<3)+(x<<1)+(ch^48);
		ch=getchar();
	}
	return x*w;
}
void write(ll x){
	if(x<0){
		putchar('-');
		x=-x;
	}
	static int sta[35];
	int top=0;
	do{
		sta[top++]=x%10,x/=10;
	}while(x);
	while(top)putchar(sta[--top]+'0');
}
int lowbit(int x){return x&(-x);}
ll n,L,R,c[100005],dp[100005],v[100005];
struct node{
	ll st,ed,S;
	bool operator <(const node &x){
		return ed<x.ed;
	}
}a[10005];
void update(ll x,ll k){
	v[x]=k;
	for(int i=x;i<=R;i+=lowbit(i)){
		c[i]=v[i];
		for(int j=1;j<lowbit(i);j*=2)c[i]=min(c[i],c[i-j]);
	}
}
ll Qmin(int l,int r){
	ll ret=LLONG_MAX;
	while(r>=l){
		ret=min(ret,v[r]);
		r--;
		for(;r-lowbit(r)>=l;r-=lowbit(r))ret=min(ret,c[r]);
	}
	return ret;
}

int main(){
	n=read();L=read()+2;R=read()+2;
	for(int i=1;i<=n;i++){
		a[i].st=read()+2;
		a[i].ed=read()+2;
		a[i].S=read();
	}
	sort(a+1,a+n+1);
	memset(dp,0x3f,sizeof(dp));
	for(int i=L;i<=100000;i++){
		update(i,dp[i]);
	}
	dp[L]=0;
	for(int i=1;i<=n;i++){
		dp[a[i].ed]=min(dp[a[i].ed],Qmin(a[i].st-1,a[i].ed-1)+a[i].S);
		update(a[i].ed,dp[a[i].ed]);
		if(a[i].ed>=R){
			if(dp[a[i].ed]>=0x3f3f3f3f3f3f3f3f)puts("-1");
			else write(dp[a[i].ed]);
			return 0;
		}
	}
	return 0;
}