#include <iostream>
#include <cstring>
#include <algorithm>
#include <queue>
 
using namespace std;
 
struct node
{
    int b, e;
    int t;
    friend bool operator < (node a, node b)
    {
        return a.e<b.e;
    }
}se[5005];
 
bool vis[30005];
 
int main()
{
    int n, h;
    int ans;
    cin>>n>>h;
    memset(vis, 0, sizeof(vis));
    for(int i=1; i<=h; i++)
    {
        cin>>se[i].b>>se[i].e>>se[i].t;
    }
    sort(se+1, se+h+1);
    ans=0;
    for(int i=1; i<=h; i++)
    {
        int cnt=0;
        for(int j=se[i].b; j<=se[i].e; j++)
        {
            cnt+=vis[j];
        }
        for(int j=se[i].e; j>=se[i].b && cnt<se[i].t; j--)
        {
            if(!vis[j])
            {
                vis[j]=1;
                cnt++;
                ans++;
            }
        }
    }
    cout<<ans<<endl;
    return 0;
}