from sys import maxint
def solve(n, L):
D = [ [maxint]*(2*i + 1) for i in range(n+1)]
D[0][0] = 0
for i in range (n):
for j in range(2*i +1):
if i+1 in L:
D[i+1][j] = D[i][j]
continue
D[i+1][j] = min(D[i+1][j], D[i][j]+10000)
for k in range(1, 4):
if i + k > n: break
D[i+k][j+1] = min(D[i+k][j+1], D[i][j]+25000)
for k in range(1, 6):
if i + k > n: break
D[i+k][j+2] = min(D[i+k][j+2], D[i][j]+37000)
if j >= 3:
D[i+1][j-3] = min(D[i+1][j-3], D[i][j])
return min(D[n])
def main():
n, k = map(int, raw_input().split())
L = map(int, raw_input().split())
print solve(n, L)
return
main()
