It is not necessary a rectangle. Try

5
11111
11011
11011
10010
00000

Yes

and all its rotations.

BTW, to read you can use

#define F(i,n) for(int i = 0; i < n; ++i)
int n;
vector<string> s;
[...]
cin >> n;
s.resize(n, string(n,' '));
F(i,n) cin >> s[i];

and AC at 0.046 second.

... whereas

F(i,n) { string str; cin >> str; s.push_back(str); }

results in 0.109 seconds and 500 KB of wasted memory.