import sys


def input(): return sys.stdin.readline().rstrip('\n')


def main():
    n = int(input())
    *a, = map(int, input().split())
    M = 10**9+7

    def t(x):
        return [(x[i]+x[i+1]) % M for i in range(len(x)-1)]
    for i in range(n-1):
        a = t(a)
    print(a[0])


if __name__ == '__main__':
    main()