#include <bits/stdc++.h>
#define pb push_back
#define ll long long
using namespace std;
const int N = 1e5 + 5;
const int M = 3e5 + 5;
const long long LL = 1e18;
ll ans;
map<ll, ll> dp[N][2];
vector<pair<ll, ll>> pref[N];
vector<int> wys[N];
bool zero[N];
ll max_weights(int n, int m, vector<int>X, vector<int>Y, vector<int>Z){
cin>>n>>m;
for(int i=0;i<m;i++){
pref[X[i]].pb({Y[i], Z[i]});
if(Y[i]==0) zero[X[i]]=true;
wys[X[i]].pb(Y[i]);
}
for(int i = 0; i < n; ++i) {
wys[i].pb(n);
if(!zero[i])wys[i].pb(0);
sort(wys[i].begin(), wys[i].end());
}
for(int i=0;i<n;i++){
sort(pref[i].begin(), pref[i].end());
ll suma=0;
for(int j=0;j<pref[i].size();j++) {
suma+=pref[i][j].second;
pref[i][j].second = suma;
}
pref[i].insert(pref[i].begin(), make_pair(-1, 0));
}
for(int i=1;i<n;i++){
vector<pair<ll, ll>> spr1, spr2;
for(ll pom : wys[i-1]){
dp[i][0][0]=max({dp[i][0][0], dp[i-1][0][pom], dp[i-1][1][pom]});
dp[i][1][0]=max({dp[i][1][0], dp[i-1][0][pom], dp[i-1][1][pom]});
ll res=0;
if(!spr1.empty()) res=spr1.back().second;
auto it = upper_bound(pref[i-1].begin(), pref[i-1].end(), make_pair(pom-1, LL));
it--;
res=max(res, dp[i-1][0][pom]-it->second);
spr1.pb({pom, res});
}
reverse(wys[i-1].begin(), wys[i-1].end());
for(ll pom : wys[i-1]){
ll res=0;
if(!spr2.empty()) res=spr2.back().second;
auto it = upper_bound(pref[i].begin(), pref[i].end(), make_pair(pom-1, LL));
it--;
res = max(res, dp[i - 1][0][pom] + it->second);
res = max(res, dp[i - 1][1][pom] + it->second);
spr2.pb({pom, res});
}
reverse(spr2.begin(), spr2.end());
for(ll pom : wys[i]){
auto op1 = upper_bound(spr1.begin(), spr1.end(), make_pair(pom, LL));
op1--;
auto op2 = lower_bound(spr2.begin(), spr2.end(), make_pair(pom, -LL));
auto tmp1 = lower_bound(pref[i-1].begin(), pref[i-1].end(), make_pair(pom, LL));
tmp1--;
dp[i][0][pom]=max(dp[i][0][pom], op1->second + tmp1->second);
auto tmp2 = lower_bound(pref[i].begin(), pref[i].end(), make_pair(pom, LL));
tmp2--;
dp[i][1][pom]=max(dp[i][1][pom], op2->second - tmp2->second);
}
}
for(int i=0;i<n;i++){
ans = max({ans, dp[n-1][0][i], dp[n-1][1][i]});
}
return ans;
}
