求助，不知道为什么会WA第二和第五个点

#include <bits/stdc++.h>
using namespace std;
const int N = 5e7+1;
int n, p, x, y, z, a[N], minx;
int main() {
 	ios :: sync_with_stdio (false);
	cin >> n >> p;
	for (int i = 1; i <= n; i ++ )
		cin >> a[i], a[i] -= a[i - 1];
	for (int i = 1; i <= p; i ++ ) {
		cin >> x >> y >> z;
		a[x] += z;
		a[y + 1] -= z;
	}
	minx = a[1];
	for (int i = 2; i <= n; i ++ ) {
		a[i] += a[i - 1];
		minx = min (minx, a[i]);
	}
	cout << minx << endl;
 	return 0;
}