gistfile1.txt

n = int(input()) # length of list
l = input().split(" ") # Number list
for i in range(n-1):
    y = []
    if len(l) == 1:
        break
    for j in range(len(l) - 1):
        y.append(int(l[j+1]) - int(l[j])) # subtraction of elements
    l = y
print(l[0] % ((10**9)+7)) # remain