N = int(input())
Y = list(map(int, input().split()))
Y.sort()
INF = 1 << 60

D = [INF]
for i in range(N - 1):
    D.append(Y[i + 1] - Y[i])
D.append(INF)

ans = 0
p = 0
while p < N:
    if D[p] > D[p + 1]:
        ans += D[p + 1]
        p += 2
    else:
        ans += D[p]
        D[p + 1] -= D[p]
        p += 1

print(ans)