---

**Задача 11**

```python
n = int(input())
a = [list(map(int, input().split())) for _ in range(n)]

d1 = {a[i][i] for i in range(n)}
d2 = {a[i][n - 1 - i] for i in range(n)}

p = set()
for r in a:
    s = set()
    for x in r:
        if x in s:
            p.add(x)
        s.add(x)

print(d1 & d2 & p)
```

**Задача 12**

```python
s = input().split()
d = {tuple(x.split('-')) for x in s}

t = sorted({(a, b) for a, b in d if (b, a) in d and a < b})
o = sorted({(a, b) for a, b in d if (b, a) not in d})

print("Двусторонние:", t)
print("Односторонние:", o)
```