/**
_ _ __ _ _ _ _ _ _
|a ||t ||o d | |o |
| __ _| | _ | __| _ |
| __ |/_ | __ /__\ / _\|
**/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N_MAX = 100000;
const int M_MAX = 300000;
int N, M;
int X[M_MAX + 2], Y[M_MAX + 2], W[M_MAX + 2];
vector <int> onX[N_MAX + 2];
ll Fen[N_MAX + 2];
vector <int> updi;
void init () {
while (updi.empty() == false) {
Fen[updi.back()] = 0;
updi.pop_back();
}
}
void update (int pos, ll val) {
for (int i = pos; i <= N; i += i & -i) {
updi.push_back(i);
Fen[i] = max(Fen[i], val);
}
}
ll query (int pos) {
ll val = 0;
for (int i = pos; i >= 1; i -= i & -i) {
val = max(val, Fen[i]);
}
return val;
}
ll dp[M_MAX + 2][2];
ll mxdp[N_MAX + 2];
ll max_weights (int _N, int _M, vector <int> _X, vector <int> _Y, vector <int> _W) {
N = _N; M = _M;
for (int i = 1; i <= M; i++) {
X[i] = _X[i - 1] + 1;
Y[i] = _Y[i - 1] + 1;
W[i] = _W[i - 1];
onX[X[i]].push_back(i);
}
for (int x = 1; x <= N; x++) {
if (x < N) {
init();
for (int i : onX[x - 1]) {
update(Y[i], dp[i][0]);
}
for (int i : onX[x]) {
dp[i][0] = query(Y[i] - 1) + W[i];
}
}
if (x > 1){
init();
for (int i : onX[x - 1]) {
update((N - Y[i] + 1), dp[i][1]);
}
for (int i : onX[x]) {
dp[i][1] = query((N - Y[i] + 1) - 1) + W[i];
}
}
if (x >= 2) {
for (int i : onX[x]) {
dp[i][0] = max(dp[i][0], mxdp[x - 2] + W[i]);
dp[i][1] = max(dp[i][1], mxdp[x - 2] + W[i]);
}
}
mxdp[x] = mxdp[x - 1];
for (int i : onX[x]) {
mxdp[x] = max({mxdp[x], dp[i][0], dp[i][1]});
}
}
return mxdp[N];
}
