Buy tickets

n = int(input())
inf = 3601
a, b, c = [inf] * (n+1), [inf] * (n+1), [inf] * (n+1)
for i in range(1, n+1):
  a[i], b[i], c[i] = map(int, input().split())

dp = [0, a[1]] + [inf] * n

for i in range(2, n+1):
  dp[i] = min(dp[i-1] + a[i], dp[i-2] + b[i-1], dp[i-3] + c[i-2])

print(dp[n])