N, M = map(int,input().split())
not_visited_days = [True]*(N+1)
if M:
for k in list(map(int,input().split())):
not_visited_days[k] = False
INF = float('inf')
dp = [[INF for _ in range(40)] for _ in range(105)]
dp[0][0] = 0
for day in range(N):
for coupon in range(37):
if not not_visited_days[day+1]:
dp[day+1][coupon] = min(dp[day+1][coupon],dp[day][coupon])
dp[day+1][coupon] = min(dp[day+1][coupon],dp[day][coupon] + 10000)
dp[day+3][coupon+1] = min(dp[day+3][coupon+1],dp[day][coupon] + 25000)
dp[day+5][coupon+2] = min(dp[day+5][coupon+2],dp[day][coupon] + 37000)
for coupon in range(39,2,-1):
dp[day+1][coupon-3] = min(dp[day+1][coupon-3],dp[day][coupon])
print(min(dp[N]))