n, v = map(int, input().split())
C = list(map(int, input().split()))
ans = sum(C)
v -= n
if v <= 0:
    print(ans)
    exit()

for i in range(1, n):
    C[i] += C[i - 1]
D = [c / i for i, c in enumerate(C, 1)]
i = D.index(min(D))
if v >= 20000:
    x = (v - 20000) // (i + 1)
    ans += x * C[i]
    v -= x * (i + 1)

dp = [1 << 60] * (v + 1)
dp[0] = 0
for i, c in enumerate(C, 1):
    for j in range(i, v + 1):
        dp[j] = min(dp[j], dp[j - i] + c)
ans += dp[-1]
print(ans)