#define _CRT_SECURE_NO_WARNINGS 1
#pragma warning(disable:6031)
#include <iostream>
#include <algorithm>
#include <cstdio>
using namespace std;
int n, m, r, d, s, t;
int arr[1000000 + 10];
int b[1000000 + 10];
int main()
{
	cin >> n >> m;
	for (int i = 1; i <= n; i++)
		scanf("%d", &arr[i]);
	for (int i = 1; i <= n; i++)
		b[i] = arr[i] - arr[i - 1];
	int ss = 0;
	while (++ss < m)
	{
		scanf("%d %d %d", &d, &s, &t);
		b[s] -= d;
		b[t + 1] += d;
		for (int i = 1; i <= n; i++)
		{
			if ((arr[i] = arr[i - 1] + b[i]) < 0)
			{
				printf("-1\n");
				cout << ss << endl;
				exit(0);
			}
		}
	}
	if (ss== m)
		cout << '0' << endl;
	return 0;
}