//2023/4/1
#include<bits/stdc++.h>
#define int long long 
using namespace std;
const int MAXN=1e6+10;
int num,ans;
struct house{
	int b;
	int e;
	int t;
}a[50010];
bool vis[300100];
bool cmp(house x,house y)
{
	return x.e<y.e;
}
signed main()
{
	int n,m;
	cin>>n>>m;
	for (int i=1;i<=m;i++)
	{
		cin>>a[i].b>>a[i].e>>a[i].t;
	}
	sort(a+1,a+1+m,cmp);
	for (int i=1;i<=n;i++)
	{
		for (int j=a[i].b;j<=a[i].e;j++)
		{
			if(vis[j]==1)
			{
				a[i].t--;
			}
		}
		for (int j=a[i].e;j>=a[i].b;j--)
		{
			if(a[i].t<=0)
			{
				break;
			}
			if (vis[j]==0)
			{
				vis[j]=1;
				a[i].t--;
				ans++;
			} 
		} 
	}
	cout<<ans<<endl;
	return 0;
}