#include<bits/stdc++.h>
using namespace std;
#define int long long
int  day[10001000],r[10001000],d[10001000],s[10001000],t[10001000],book[10001000];
int kkk=0;
inline long long read() {
	long long x=0,f=1;
	char c=getchar();
	while(c<'0'||c>'9') {
		if(c=='-')f=-1;
		c=getchar();
	}
	while(c>='0'&&c<='9') {
		x=x*10+c-'0';
		c=getchar();
	}
	return x*f;
}
signed main() {
	///freopen("P1083.in","r",stdin);
	int n,m;
	cin>>n>>m;
	for(int i=1; i<=n; i++) {
		cin>>r[i];
	}
	for(int i=1; i<=m; i++) {
		d[i]=read();
		s[i]=read();
		t[i]=read();
		day[s[i]]+=d[i];
		day[t[i]+1]-=d[i];
	}
	int flag=0;
	for(int i=1; i<=n; i++) {
		day[i]+=day[i-1];
		if(r[i]<day[i]) {
			flag=1;
			if(!kkk) {
				cout<<-1<<endl;
				kkk++;
			}

			int hhh=r[i];
			int ghgh=0;
			for(int j=1; j<=n; j++) {
				if(s[j]<=i&&i<=t[j]) {
					hhh-=d[j];
					if(hhh<=0) {
						ghgh=1;
						//cout<<j<<endl;
						book[j]=1;
					}
				}

			}
		}

	}
	/*if(flag){
		cout<<"-1"<<endl;
	}*/
	if(flag){
		for(int i=1;i<=n;i++){
			if(book[i]){
			cout<<i+4;
			return 0;
			}
			
		} 
	} 
	if(!flag) {
		cout<<0<<endl;
	}
	return 0;
}