#include<bits/stdc++.h>
using namespace std;
int n,h,ans,a[300005],x,y,k,yy;
struct node{
	int b,e,t;
}s[50005];
int cmp(node a,node b)
{
	return a.e<b.e;
}
int main()
{
    freopen("plant_tree.in","r",stdin);
    freopen("plant_tree.out","w",stdout); 
	scanf("%d %d",&n,&h);
	for(int i=1;i<=h;i++)
		scanf("%d %d %d",&s[i].b,&s[i].e,&s[i].t);
	sort(s+1,s+h+1,cmp);
	for(int i=1;i<=h;i++)
	{
		x=y=0;
		for(int j=s[i].b;j<=s[i].e;j++)
			if(a[j]==1)
				x++;
		y=s[i].t-x;
		if(y>0)
		{
			for(int j=s[i].e;y>0&&j>=s[i].b;j--)
			{
				if(a[j]==0)
				{
					a[j]=1;
					ans++;
					y--;
				}
			}
		}
	}
	printf("%d",ans);
	return 0;
}