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
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
#include <algorithm>
#include <bitset>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <vector>

using namespace std;

#define PB push_back
#define MP make_pair
#define F first
#define S second
#define ALL(x) (x).begin(),(x).end()
#define SIZE(x) (int)(x).size()
#define CLEAR(tab) memset(tab, 0, sizeof(tab))
#define REP(x, n) for(int x = 0; x < (n); x++)
#define FOR(x, b, e) for(int x = (b); x <= (e); x++)
#define FORD(x, b, e) for(int x = (b); x >= (e); x--)
#define VAR(v, n) __typeof(n) v = (n)
#define FOREACH(i, c) for(VAR(i, (c).begin()); i != (c).end(); ++i)
#define DEBUG(fmt, ...) fprintf(stderr, fmt, ##__VA_ARGS__)

typedef long long int LL;
typedef pair<int,int> PII;
typedef vector<int> VI;

const int MXN = 500010;
const int C = 2 * 262144;
const int INF = 1000000001;
const int MOD = 1000000007;

int n, c;
int a[MXN], w[MXN];
LL tree[2 * C + 10];

void add(int x, LL val) {
    x += C;
    tree[x] = max(tree[x], val);
    x /= 2;
    while(x) {
        tree[x] = max(tree[2 * x], tree[2 * x + 1]);
        x /= 2;
    }
}

LL maks(int x) {
    x += C;
    LL res = 0;
    while(x) {
        if(x % 2)
            res = max(res, tree[x - 1]);
        else
            res = max(res, tree[x + 1]);
        x /= 2;
     }
    return res;
}

void test() {
    scanf("%d %d", &n, &c);
    FOR(i, 1, n) {
        scanf("%d %d", &a[i], &w[i]);
    }

    FOR(i, 1, n) {
        int iter = i;
        vector<pair<int, LL> > vec;
        while(iter <= n && a[i] == a[iter]) {
            LL res1 = maks(w[iter]) - c + a[iter];
            LL res2 = tree[C + w[iter]] + a[iter];
            vec.PB({w[iter], max(res1, res2)});
            iter++;
        }
        FOREACH(it, vec)
            add(it -> F, it -> S);
        i = iter - 1;
    }

    printf("%lld\n", max(maks(1), tree[C + 1]));
}

int main() {
	int te = 1;
	//scanf("%d", &te);
	while(te--)
		test();
	return 0;
}