17404.py

n = int(input())
arr = [list(map(int, input().split())) for _ in range(n)]
ans = float('inf')

for i in range(3):
  dp = [[float('inf')]*3 for _ in range(n)]
  dp[0][i] = arr[0][i]
  for j in range(1, n):
    dp[j][0] = min(dp[j-1][1], dp[j-1][2]) + arr[j][0]
    dp[j][1] = min(dp[j-1][2], dp[j-1][0]) + arr[j][1]
    dp[j][2] = min(dp[j-1][0], dp[j-1][1]) + arr[j][2]
  
  for j in range(3):
    if i != j:
      ans = min(ans, dp[n-1][j])

print(ans)