rt.

#include<bits/stdc++.h>
using namespace std;
int n,h,ans,vis[30005];
struct Data{
	int l,r,t;
	bool operator <(const Data tmp) const{return l<tmp.l;}
}data[5005];
int main(){
	scanf("%d%d",&n,&h);
	for(int i=1;i<=h;i++) scanf("%d%d%d",&data[i].l,&data[i].r,&data[i].t);
	sort(data+1,data+h+1);
	for(int i=1,cnt;i<=h;i++){
		cnt=0;
		for(int j=data[i].l;j<=data[i].r;j++) cnt+=vis[j];
		if(cnt>=data[i].t) continue;
		for(int j=data[i].r;j>=data[i].l;j--){
			if(!vis[j]) vis[j]=1,cnt++,ans++;
			if(cnt>=data[i].t) break;
		}
	}
	printf("%d",ans);
	return 0;
}