612 B | 612 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
BLANK = " "
#inp = input
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
n = ii()
l = [0] + mii() + [0]
ans = 2 * n
for i in range(n + 1):
ans += 2 * l[i]
ans += abs(l[i + 1] - l[i])
p(ans)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()