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#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define vc vector
#define st first
#define nd second
#define pll pair<ll, ll>
#define sz(a) (ll)a.size()
#define all(a) a.begin(), a.end()
#define pu push
#define pub push_back
#define pob pop_back
#define em emplace
#define emb emplace_back
const ll INF = 1e18;

struct Tree {
	ll base;
	vc<ll> t;

	Tree(ll n) {
		base = 1;
		while (base < n)
			base *= 2;
		t.assign(2 * base, INF);
	}

	void upd(ll i, ll x) {
		i += base;
		t[i] = x;
		i /= 2;
		while (i >= 1) {
			t[i] = min(t[2 * i], t[2 * i + 1]);
			i /= 2;
		}
	}

	void add(ll i, ll x) {
		i += base;
		t[i] += x;
		i /= 2;
		while (i >= 1) {
			t[i] = min(t[2 * i], t[2 * i + 1]);
			i /= 2;
		}
	}

	ll query(ll l, ll r) {
		ll ret = INF;
		l += base - 1;
		r += base + 1;
		while (l + 1 < r) {
			if (l % 2 == 0)
				ret = min(ret, t[l + 1]);
			if (r % 2 == 1)
				ret = min(ret, t[r - 1]);
			l /= 2;
			r /= 2;
		}
		return ret;
	}
};

ll n, m, N, f;
vc<vc<ll>> a, prf;

ll fct(ll x) {
	ll ret = 1;
	for (ll i = 1; i <= x; i++)
		ret *= i;
	return ret;
}

void input() {
	cin >> m >> n;
	f = fct(m);
	N = f * n;
	a.assign(m, vc<ll>(N, 0));
	for (ll i = 0; i < m; i++) {
		string str;
		cin >> str;
		for (ll j = 0; j < n; j++) {
			if (str[j] == '.')
				continue;
			for (ll k = j * f; k < (j + 1) * f; k++)
				a[i][k] = 1;
		}
	}

	prf.assign(m, vc<ll>(N + 1, 0));
	for (ll i = 1; i <= N; i++)
		for (ll j = 0; j < m; j++)
			prf[j][i] = prf[j][i - 1] + a[j][i - 1];
}

bool check(ll s) {
	vc<ll> p(m);
	iota(all(p), 0);
	do {
		Tree tree(N);
		for (ll i = 0; i < N; i++) {
			ll cnt = 0;
			for (ll j = 0; j < m; j++)
				if (a[j][i] == 0)
					cnt++;
			tree.upd(i, cnt - 1);
		}
		if (tree.t[1] < 0)
			continue;

		bool good = true;
		ll j = 0;
		for (ll i : p) {
			bool found = false;
			while (j + s <= N) {
				if (tree.query(j, j + s - 1) <= 0 or prf[i][j + s] - prf[i][j] > 0) {
					j++;
					continue;
				}
				found = true;
				for (ll k = j; k < j + s; k++)
					tree.add(k, -1);
				break;
			}
			if (not found) {
				good = false;
				break;
			}
		}
		if (good)
			return true;
	} while (next_permutation(all(p)));
	return false;
}

ll binsearch() {
	ll l = -1, r = N;
	while (l < r) {
		ll s = (l + r + 1) / 2;
		if (check(s))
			l = s;
		else
			r = s - 1;
	}
	return l;
}

void output(ll x) {
	if (x == -1) {
		cout << "-1\n";
		return;
	}
	ll g = gcd(x, f);
	x /= g;
	f /= g;
	cout << x << "/" << f << "\n";
}

void program() {
	input();
	output(binsearch());
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);
	ll T = 1;
	while (T--)
		program();
	return 0;
}