1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define imie(x...) cerr << "[" #x "]: ", [](auto... $) {((cerr << $ << "; "), ...); }(x), cerr << '\n'
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
const int mod=1e9+7;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
const ll INF = -1e18;

struct T {
    int a;
    int w;
};

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0);
 
    int n, c;
    cin >> n >> c;
    vector<T> v(n);
    for(int i = 0; i < n; i++){
        cin >> v[i].a >> v[i].w;
    }
    int idx = n - 1;
    vector<ll> best(500001, INF);
    ll ans2 = INF, ans = 0;
    while(idx >= 0){
        int siz = v[idx].a;
        vector<ll> dp;
        vector<int> g;
        while(idx >= 0 && v[idx].a == siz){
            int w = v[idx].w;
            ll cs = best[w];
            ll cd = (ans2 == INF ? INF : ans2 - c);
            ll kand = max({0LL, cs, cd});
            dp.push_back(siz + kand);
            g.push_back(w);
            ans = max(ans, siz + kand);
            idx--;
        }
        for(int i = 0; i < dp.size(); i++){
            int p = g[i];
            best[p] = max(best[p], dp[i]);
            ans2 = max(ans2, dp[i]);
        }
    }
 
    cout << ans << "\n";
    return 0;
}