/*
ID: huseyna2
TASK: barn1
LANG: C++
*/
#include <bits/stdc++.h>
#define MAX 300001
#define INF 10000000001
#define MOD 1000000007
#define mp make_pair
#define pb push_back
#define ins insert
#define f first
#define s second
using namespace std;
typedef long long ll;
typedef pair<ll,ll> pll;
ll n,t,r,m,k,res,x,y,sum;
string s;
set<pll> a[MAX];
set<ll> b[MAX];
bool comp(tuple <ll,ll,ll> x,tuple<ll,ll,ll> y){
return get<0>(x)>get<0>(y);
}
void solve(){
ll dp[n+1];
dp[0]=0;
dp[1]=0;
ll h=n,sum=0;
if(b[0].size()!=0){
h=*b[0].begin();
for(auto x:a[0]){
sum+=x.second;
}
dp[1]=sum;
}
for(int i=2;i<=n;i++){
dp[i]=dp[i-1];
if(b[i-1].size()!=0){
ll j;
sum=0;
j=distance(b[i-1].begin(),b[i-1].lower_bound(h-1));
if(j==0){
h=n;
}
else{
h=*b[i-1].begin();
}
auto it=a[i-1].begin();
ll z=0;
while(it!=a[i-1].end() && z<j){
dp[i]+=(*it).second;
++it;
z++;
}
sum=0;
for(auto x:a[i-1]){
sum+=x.second;
}
if(sum+dp[i-2]>dp[i]){
dp[i]=sum+dp[i-2];
h=*b[i-1].begin();
}
}
else{
h=n;
}
}
cout << dp[n] << "\n";
}
int main(){
t=1;
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
//cin >> t;
while(t--){
cin >> n >> m;
for(int i=0;i<m;i++){
ll k1,k2,k3;
cin >> k1 >> k2 >> k3;
a[k1].insert(make_pair(n-k2-1,k3));
b[k1].insert(n-k2-1);
}
solve();
}
}
/*
freopen("input.txt","r",stdin);
freopen("output.txt","w",stdout);
ifstream fin("template.in");
ofstream fout("template.out");
*/
/*
freopen("input.txt","r",stdin);
freopen("output.txt","w",stdout);
ifstream fin("template.in");
ofstream fout("template.out");
*/
/*
ll b[51][51];
b[0][0] = 1;
for (int n = 1; n <= 50; ++n){
b[n][0] = b[n][n] = 1;
for (int k = 1; k < n; ++k)
b[n][k] = b[n - 1][k - 1] + b[n - 1][k];
}
*/
Compilation message
/usr/bin/ld: /tmp/ccMxxra9.o: in function `main':
grader.cpp:(.text.startup+0x0): multiple definition of `main'; /tmp/ccTyKHPb.o:fish.cpp:(.text.startup+0x0): first defined here
/usr/bin/ld: /tmp/ccMxxra9.o: in function `main':
grader.cpp:(.text.startup+0x25e): undefined reference to `max_weights(int, int, std::vector<int, std::allocator<int> >, std::vector<int, std::allocator<int> >, std::vector<int, std::allocator<int> >)'
collect2: error: ld returned 1 exit status
