#include <bits/stdc++.h>
using namespace std;
const int N=50010;
struct cow{
    int st,ed,id;
}a[N];
bool cmp(cow a,cow b){
	return a.ed<b.ed;
}
int n,m,x,ans;
bool bj[N];
int main(){
    freopen("plant_tree.in","r",stdin);
    freopen("plant_tree.out","w",stdout);    
    cin>>n>>m;
    for(int i=1;i<=m;i++){
        cin>>a[i].st>>a[i].ed>>a[i].id;
    }
    sort(a+1,a+m+1,cmp);
    for(int i=1;i<=m;i++){
		x=0;
		for(int j=a[i].st;j<=a[i].ed;j++){
			if(bj[j]){
			    x++;
			}
		}
		for(int j=a[i].ed;j>=a[i].st;j--){
			if(x>=a[i].id){
				break;
			}
			if(!bj[j]){
				x++;
				ans++;
				bj[j]=1;
			}
		}
	}	
	cout<<ans;
    
    return 0;
}