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
55
56
57
58
59
60
61
62
63
64
65
#include <bits/stdc++.h>

using namespace std;
using LL = long long;
#define FOR(i, l, r) for(int i = (l); i <= (r); ++i)
#define REP(i, n) FOR(i, 0, (n) - 1)
#define ssize(x) int(x.size())

template<class A, class B> auto &operator<<(ostream &o, pair<A, B> p) {
    return o << '(' << p.first << ", " << p.second << ')';
}

template<class T> auto operator<<(ostream &o, T x) -> decltype(x.end(), o) {
    o << '{'; int i = 0; for (auto e : x) o << (", ")+2*!i++ << e;
    return o << '}';
}

#ifdef DEBUG
#define debug(x...) cerr << "[" #x "]: ", [](auto... $) {((cerr << $ << "; "), ...); }(x), cerr << '\n';
#else
#define debug(...) {}
#endif


int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int n;
    LL c;
    cin >> n >> c;
    vector<LL> a(n);
    vector<int> w(n);
    int mx = 0;
    REP(i, n) {
        cin >> a[i] >> w[i];
        mx = max(mx, w[i]);
    }

    vector<LL> dp(mx + 1);
    map<pair<int, int>, bool> vis;
    LL max_dp = 0;
    for (int i = n - 1; i >= 0;) {
        int j = i;
        LL new_max = 0;
        while (j >= 0 && a[j] == a[i]) {
            if (vis[{a[j], w[j]}]) {
                j--;
                continue;
            }
            vis[{a[j], w[j]}] = true;

            dp[w[j]] = a[j] + max(dp[w[j]], max_dp - c);
            new_max = max(new_max, dp[w[j]]);
            j--;
        }

        max_dp = max(max_dp, new_max);
        i = j;
    }

    cout << max_dp << '\n';

    return 0;
}