from math import ceil

n, d, t = list(map(int, input().split()))
mas = [[int(j) for j in input().split()] for i in range(n)]
counter = 1
pos = 0
for i in range(n):
    if mas[i][0] - pos > d:
        if (mas[i][0] - pos) % d == 0:
            counter += (mas[i][0] - pos) // d
            pos = mas[i][0]

        else:
            counter += (mas[i][0] - pos) // d
            pos += (mas[i][0] - pos) // d * d

        if mas[i][1] - pos > d:
            pos = mas[i][0] + d
            counter += 2
        else:
            pos += d
            counter += 1
    else:
        if mas[i][1] - pos > d:
            pos = mas[i][0] + d
            counter += 2
        else:
            pos += d
            counter += 1
if pos < t:
    counter += ceil((t - pos) / d)
print(counter)