#include<bits/stdc++.h>
using namespace std;
const int maxn=1e6+5;
unsigned long long a[maxn];
struct jk{
	unsigned long long d,s,t;
}b[maxn];
unsigned long long diff[maxn];
unsigned long long n,m;
bool cheak(int mid){
	for(int i=1;i<=m;i++){
		diff[i]=0;
	}
	for(int i=1;i<=mid;i++){
		diff[b[i].s]+=b[i].d;
		diff[b[i].t+1]-=b[i].d;
	}
	int sum=0;
	for(int i=1;i<=n;i++){
		sum+=diff[i];
		if(sum>a[i]){
			return 0;
		}
	} 
	return 1;
}
int main(){
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	for(int i=1;i<=m;i++){
		cin>>b[i].d>>b[i].s>>b[i].t;
	}
	if(cheak(m)){
		cout<<"0";
		return 0;
	}
	int l=0,r=m+1,mid;
	while(l<r){
		mid=(l+r)>>1;
		if(cheak(mid)){
			l=mid+1;
		}
		else{
			r=mid;
		}
	}
	cout<<"-1"<<endl;
	cout<<l;
	return 0;
}