Untitled

f = open("27.2.B.txt")
n, m = map(int, f.readline().split())
a = [0]*10000000
for s in f:
    km, litr = map(int, s.split())
    if litr % 15 == 0:
        a[km] = litr // 15
    else:
        a[km] = litr // 15 + 1
result = [sum(a[0:2*m + 1])]
x = result[-1]
for i in range(m + 1, n - m):
    x += a[i + m] - a[i - m - 1]
    if a[i] != 0:
        result.append(x)
        
    
print(max(result))