#include<bits/stdc++.h>
using namespace std;

const int MAXN=1000005;
int n,m,cf[MAXN],re[MAXN],ne[MAXN],d[MAXN],l[MAXN],r[MAXN];

bool check(int t)
{
    memset(cf,0,sizeof(cf));
    for(int i=1;i<=t;i++)
    {
        cf[l[i]]+=d[i];
        cf[r[i]+1]-=d[i];
    }
    for(int i=1;i<=n;i++)
    {
        ne[i]=ne[i-1]+cf[i];
        if(ne[i]>re[i])
            return false;
    }
    return true;
}

int main()
{
    ios::sync_with_stdio(false);
    cin>>n>>m;
    for(int i=1;i<=n;i++)
        cin>>re[i];
    for(int i=1;i<=m;i++)
        cin>>d[i]>>l[i]>>r[i];
    int be=1,en=m;
    if(check(m))
    {
        cout<<0;
        return 0;
    }
    while(be<en)
    {
        int mid=be+(en-be)/2;
        if(check(mid))
            be=mid+1;
        else
            en=mid;
    }
    printf("-1\n%d",be);
    return 0;
}