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
93
94
95
96
97
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

#define int long long
#define pii pair<int, int>
#define fi first
#define se second

const int INF = 1e15 + 7;
const int MAXN = 5e5 + 7;
const int MAX = 5e5;
const int base = 1<<20;

int dp[MAXN];
pair<int, int> tab[MAXN];

int tree[2 * base];

void update(int pos, int val){
	
	pos += base;
	tree[pos] = max(tree[pos], val);
	pos /= 2;
	
	while(pos > 1){
		
		tree[pos] = max(tree[2 * pos], tree[2 * pos + 1]);
		pos /= 2;	
	}
}


int query(int a, int b){
	
	if(a > b) return 0;
	
	a += base;
	b += base;
	int ans = max(tree[a], tree[b]);
	
	while(a/2 != b/2){
		
		if(a%2 == 0) ans = max(ans, tree[a + 1]);
		if(b%2 == 1) ans = max(ans, tree[b - 1]);
		a /= 2; b /= 2;
	}
	
	return ans;
}


void solve(){
	
	int n, c;
	cin >> n >> c;
	
	for(int i = 1; i <= n; i++) cin >> tab[i].fi >> tab[i].se;
	sort(tab + 1, tab + n + 1);
	
	for(int i = 1; i <= n; i++){

		dp[i] = max(tab[i].fi, query(tab[i].se, tab[i].se) + tab[i].fi);
		dp[i] = max(dp[i], query(1, tab[i].se - 1) + tab[i].fi - c);
		dp[i] = max(dp[i], query(tab[i].se + 1, MAX) + tab[i].fi - c);

		if(tab[i].fi != tab[i + 1].fi){
			
			int j = i;
			while(j > 0 && tab[j].fi == tab[i].fi){
				
				update(tab[j].se, dp[j]);
				j--;
			}
		}
	}
	
	int mx = 0;
	for(int i = 1; i <= n; i++) mx = max(mx, dp[i]);
	cout << mx << '\n';
}

bool multi = 0;

signed main(){
	
	ios_base::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);
	
	int t = 1;
	if(multi) cin >> t;
	while(t--) solve();
	
	return 0;
}