from collections import deque
class CHT(): # Convex Hull Trick, Sorted Lines, Sorted Queries, Min Query
    # add_line は a の降順
    # query は x の昇順

    def __init__(self):
        self.Q = deque()
    
    def calc(self, f, x):
        return f[0] * x + f[1]
    
    def check(self, f1, f2, f3):
        return (f2[0] - f1[0]) * (f3[1] - f2[1]) >= (f2[1] - f1[1]) * (f3[0] - f2[0])
    
    def add_line(self, a, b):
        f = (a, b)
        while len(self.Q) >= 2 and self.check(self.Q[-2], self.Q[-1], f):
            self.Q.pop()
        self.Q.append(f)
    
    def query(self, x):
        while len(self.Q) >= 2 and self.calc(self.Q[0], x) >= self.calc(self.Q[1], x):
            self.Q.popleft()
        return self.calc(self.Q[0], x)

class LiChaoTree:
    # Min Query
    def __init__(self, X): # X: 調べる可能性のある x 座標のリスト
        X = sorted(list(set(X)))
        self.inf = 10 ** 18
        self.n = 1 << (len(X) - 1).bit_length()
        self.X = X + [self.inf] * (self.n - len(X))
        self.D = {a: i for i, a in enumerate(X)}
        self.lmr = [(0, 0, 0)] * self.n + [(x, x, x) for x in self.X]
        for i in range(1, self.n)[::-1]:
            self.lmr[i] = (self.lmr[i*2][0], self.lmr[i*2][2], self.lmr[i*2^1][2])
        self.F = [None] * (self.n * 2)
    
    def calc(self, f, x):
        return f[0] * x + f[1]
    
    def update(self, i, f):
        while 1:
            l, m, r = self.lmr[i]
            fi = self.F[i]
            if fi is None:
                self.F[i] = f
                return
            cl = (fi[0] - f[0]) * l + fi[1] - f[1] > 0
            cr = (fi[0] - f[0]) * r + fi[1] - f[1] > 0
            
            if cl and cr:
                self.F[i] = f
                return
            if not cl and not cr:
                return
            if (fi[0] - f[0]) * m + fi[1] - f[1] > 0:
                self.F[i], f = f, fi
                cl = not cl
            if cl:
                i *= 2
            else:
                i = i * 2 + 1
    
    def query(self, x):
        i = self.D[x] + self.n
        mi = self.inf
        while i > 0:
            if self.F[i]:
                mi = min(mi, self.calc(self.F[i], x))
            i >>= 1
        return mi
    
    def add_line(self, a, b): # y = ax + b
        f = (a, b)
        self.update(1, f)
    
    def debug(self):
        print("F =", self.F)
        print("X =", self.X)
        print("D =", self.D)
        print("lmr =", self.lmr)

import sys
input = lambda: sys.stdin.readline().rstrip()
N, C = map(int, input().split())
lct1 = LiChaoTree([i for i in range(N + 1)])
C *= 2
X = [0] * (N + 1) # i 番目の職人を使うときに i 番目の島までのコストの最小値
Y = [0] * (N + 1) # i 番目の島までのコストの最小値
I = []
Z = []
for i in range(1, N + 1):
    a, b = map(int, input().split())
    a *= 2
    b *= 2
    I.append((a, b))
    Z.append(a + C * i)
lct2 = LiChaoTree(Z)
lct2.add_line(0, 0)

for i, (a, b) in enumerate(I, 1):
    z = lct2.query(a + C * i) + b + i * a + C // 2 * (i ** 2 - i)
    X[i] = z
    lct1.add_line(a - C // 2 * (2 * i - 1), X[i] - i * a + C // 2 * (i ** 2 - i))
    Y[i] = lct1.query(i) + C // 2 * i ** 2
    
    lct2.add_line(-i, (i ** 2 + i) * C // 2 + Y[i])
print(Y[-1] // 2)