科学怪人:N = int(input())
A, B, C = [], [], []
for i in range(N):
a, b, c = list(map(int, input().split()))
A.append(a)
B.append(b)
C.append(c)
def minTime(A, B, C, N):
dp = [[float('inf'), float('inf')] for i in range(N+1)]
dp[0] = [float('inf'), 0]
for i in range(1, N+1):
dp[i][0] = min(dp[i-1][0], dp[i-1][1] + C[i-1]) + A[i-1]
dp[i][1] = min(dp[i-1][1], dp[i-1][0] + C[i-1]) + B[i-1]
return min(dp[N])
print(minTime(A,B,C,N))