#include <cstdio>
#include <iostream>
#include <cstdlib>
#include <string>
#include <cstring>
#include <cmath>
#include <vector>
#include <set>
#include <algorithm>
using namespace std;
int a,b,c,d,maxx,s,t;
bool bo[30001];
struct fun
{
	int l,m,n;
}f[5000000];	
int Compare(const void*elem1,const void*elem2)
{
	struct fun *elem3=(struct fun *)elem1;
	struct fun *elem4=(struct fun *)elem2;
	if (elem3->m != elem4-> m) return elem3->m - elem4->m;
		else return elem4->l - elem3->l;
}
int main(void)
{
	freopen("trees.in","r",stdin);
	freopen("trees.out","w",stdout);
	scanf("%d%d",&a,&b);
	for (c=0;c<b;c++) scanf("%d%d%d",&f[c].l,&f[c].m,&f[c].n);
	qsort(f,b,sizeof(fun),Compare);
	for (c=0;c<b;c++)
	{
		t=0;
		for (d=f[c].l;d<=f[c].m;d++) if (bo[d]==true) t++;
		t=f[c].n-t;
		if (t>0)
		{
			for (d=f[c].m;d>f[c].m-f[c].n;d--) 
			if (bo[d]==false) 
			{
				bo[d]=true;
				t--;
				if (t==0) break;
			}
		}
	}
	for (c=1;c<=a;c++) 
		if (bo[c]==true) s++;
	printf("%d",s);
	fclose(stdin);
	fclose(stdout);
	return 0;
}