#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define all(a) a.begin(), a.end()
#define allr(a) a.rbegin(), a.rend()
const int N = 5e2 + 1;
int vis[N][N][8], n, m, k;
char grid[N][N];
const int dr[] = {1, 1, 1, 0, 0, -1, -1, -1};
const int dc[] = {1, -1, 0, 1, -1, 1, -1, 0};
string get_path(int r, int c, int d) {
string res = "";
while (!vis[r][c][d]) {
res += grid[r][c];
vis[r][c][d] = true;
r = (r + dr[d] + n) % n;
c = (c + dc[d] + m) % m;
}
return res;
}
struct Hash {
const int M = 1e9 + 9;
const int P = 9973;
int n;
vector<ll> pw, hsh;
ll mul(ll a, ll b) {
return (a * b) % M;
}
ll add(ll a, ll b) {
return (a + b) % M;
}
ll sub(ll a, ll b) {
return (a - b + M) % M;
}
Hash(string s) {
n = s.size();
pw.push_back(1);
hsh.push_back(0);
for (int i = 1; i <= n; i++) {
pw.push_back(mul(pw.back(), P));
hsh.push_back(add(s[i - 1], mul(hsh.back(), P)));
}
}
ll get(int l, int r) {
return sub(hsh[r + 1], mul(hsh[l], pw[r - l + 1]));
}
ll merge(ll lval, ll rval, int rsize) {
return add(rval, mul(lval, pw[rsize]));
}
ll getByLen(int l, int len) {
if (len == 0) return 0;
int end = (l + len - 1) % n;
if (l <= end) return get(l, end);
return merge(get(l, n - 1), get(0, end), end + 1);
}
ll duplicate(int val, int k) {
if (k == 0) return 0;
ll ret = duplicate(val, k >> 1);
ret = merge(ret, ret, k >> 1);
if (k % 2) ret = merge(ret, val, n);
return ret;
}
ll getByStart(int i) {
return merge(get(i, n - 1), get(0, i - 1), i);
}
};
void solve() {
cin >> n >> m >> k;
for (int i = 0; i < n; i++)
for (int j = 0; j < m; j++)
cin >> grid[i][j];
map<ll, ll> mp;
for (int r = 0; r < n; r++)
for (int c = 0; c < m; c++)
for (int d = 0; d < 8; d++) {
if (vis[r][c][d]) continue;
string s = get_path(r, c, d);
Hash hsh(s);
int len = s.size();
int cnt = k / len, remain = k % len;
for (int i = 0; i < len; i++) {
ll cur = hsh.getByStart(i);
cur = hsh.duplicate(cur, cnt);
ll other = hsh.getByLen(i, remain);
cur = hsh.merge(cur, other, remain);
++mp[cur];
}
}
ll den = pow(1ll * n * m * 8, 2);
ll num = 0, sum = 0;
for (auto& [k, v] : mp) {
num += v * v;
sum += v;
}
ll GCD = gcd(num, den);
num /= GCD;
den /= GCD;
cout << num << "/" << den << endl;
}
int main() {
ios_base::sync_with_stdio(NULL);
cin.tie(NULL), cout.tie(NULL);
int t = 1;
// cin >> t;
while (t--) solve();
}
