from collections import deque

d = deque()


N, D, T = map(int, input().split())

X = deque(list(map(int, input().split())))

for _ in range(T):
    for i in range(len(X)):
        a = X[i]
        b = a - D
        c = a + D
        if not X.count(b):
            X.append(b)
        if not X.count(c):
            X.append(c)
print(len(set(X)))