n = int(input()) cost = input().split(' ')

for i in range(len(cost)): cost[i]=int(cost[i])

dp=[]

if n==1:

print(cost[0])

elif n==2: print(min(cost[0], cost[1])) else: # 初始化dp dp.append(cost[0]) dp.append(cost[1]) for i in range(3,n+1): dp.append(cost[i-1]+min(dp[i-3],dp[i-2])) print(min(dp[n-1],dp[n-2]))