def find_min_path_sum(M):
    N = len(M)
    for i in range(1, N):
        M[i][0] += M[i-1][0]
        M[0][i] += M[0][i-1]
    for i in range(1, N):
        for j in range(1, N):
            M[i][j] += min(M[i-1][j], M[i][j-1])
    return M[-1][-1]

print(find_min_path_sum([list(map(int, input().split())) for _ in range(int(input()))]))