MOD = 10**9+7
N = int(input())
A = list(map(int, input().split()))

DP = [[0] * (N) for _ in range(N)]

for i in range(N):
    for j in range(N):
        if i == 0 or j == 0:
            DP[i][j] = 1
        else:
            DP[i][j] = DP[i - 1][j] + DP[i][j - 1]
            DP[i][j] %= MOD
ans = 0
for i in range(N):
    ans += A[i] * DP[i][N - 1 - i]
    ans %= MOD

print(ans)