A, B, C = 0, 1, 2

n = int(input())
time = [list(map(int, input().split())) for i in range(n)]
min_time = [None] * n
min_time[0] = time[0][A]
if n > 1:
    min_time[1] = min(min_time[0] + time[1][A], time[0][B])
if n > 2:
    min_time[2] = min(min_time[1] + time[2][A], min_time[0] + time[1][B],
                        time[0][C])
for i in range(3, n):
    min_time[i] = min(min_time[i - 1] + time[i][A], min_time[i - 2] +
                        time[i - 1][B], min_time[i - 3] + time[i - 2][C])
print(min_time[n - 1])