#include <iostream>
#include <cstdio>
#include <cmath>
#include <algorithm>
using namespace std;
const int N=1e5+10;
int n,w,f[N],ans;
struct node{int p,t,v;}a[N];
bool cmp(node a,node b){
	return a.t<b.t;
}
int main(){
	freopen("free.in","r",stdin);
	freopen("free.out","w",stdout);
	scanf("%d %d",&w,&n);
	for(int i=1;i<=n;i++)scanf("%d %d %d",&a[i].t,&a[i].p,&a[i].v);
	sort(a+1,a+1+n,cmp);
	for(int i=1;i<=n;i++){
		f[i]=a[i].v;
		for(int j=1;j<i;j++){
			if(a[i].t-a[j].t>=abs(a[i].p-a[j].p))f[i]=max(f[i],f[j]+a[i].v);
		}
		ans=max(ans,f[i]);
	}
	printf("%d\n",ans);
	return 0;
}
/*
10 5
1 7 545
1 2 388
6 9 125
7 1 148
7 5 573
*/