#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
int main()
{
    long int n,m;
    cin>>n>>m;
    long int arr[n];
    long int k;
    int a,b;
    for (long int i=0;i<n;i++)
    arr[i]=0;
    for (long int i=0;i<m;i++)
    {
        cin>>a>>b>>k;
        for (int j=a-1;j<=b-1;j++ )
        {
            arr[j]+=k;
        }
    }
    long int max=arr[0];
    for (long int k=0;k<n;k++)
    {
        if (arr[k]>max)
        max=arr[k];
    }
    cout<<max;

    return 0;
}