#include<bits/stdc++.h>
using namespace std;

const int N = 1005;
int w, n, dp[N], mt;

struct str {
    int t, p, v;
} a[N];

bool cmp(str x, str y) { return x.t < y.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++) {
        dp[i] = a[i].v;
        for(int j = 1; j < i; j++) {
            if(abs(a[i].t - a[j].t) * 2 >= abs(a[i].p - a[j].p))
                dp[i] = max(dp[i], dp[j] + a[i].v);
        }
    }
    
    int ans = 0;
    for(int i = 1; i <= n; i++) ans = max(ans, dp[i]);
    printf("%d", ans);
    
    return 0;
}