https://www.acmicpc.net/problem/2579
import sys
n = int(sys.stdin.readline().strip())
stair =[]
stair.append(0)
ans = [0]*(n+1)
cnt = 0
for i in range(n):
stair.append(int(sys.stdin.readline().strip()))
ans[1]= stair[1]
for i in range(2,n+1):
if cnt <2:
if ((ans[i-1]+stair[i]) - (ans[i-2]+stair[i])) >= 0:
cnt+=2
else:
cnt =0
ans[i] = max(ans[i-1]+stair[i], ans[i-2]+stair[i])
else:
ans[i] = ans[i-2]+stair[i]
cnt=0
print(ans[n])
import sys
n = int(sys.stdin.readline().strip())
stair = [0]
for _ in range(n):
stair.append(int(sys.stdin.readline().strip()))
ans= [0] *(n+1)
ans[1] = stair[1]
if n>1:
ans[2] = stair[1] + stair[2]
for i in range(3,n+1):
ans[i] = max(ans[i-2], ans[i-3]+ans[i-1])+stair[i]
print(ans[n])