#include <bits/stdc++.h>
using namespace std;
const int mod = 1e9+7;
const int base = 1e9+3;
long long n,m,K;
char a[505][505];
long long Hash[505][505][32],power[32];
map<long long,long long> cnt;
long long dx[] = {0,-1,0,1,-1,-1,1,1};
long long dy[] = {-1,0,1,0,-1,1,-1,1};
long long cal(long long i,long long j,long long dir) {
long long res = 0;
for (int p = 0; p < 31; p++) {
if ((K >> p)&1) {
res = (res*power[p]+Hash[i][j][p])%mod;
i = (i+(1ll << p)*dx[dir]%m+m)%m;
j = (j+(1ll << p)*dy[dir]%n+n)%n;
}
}
return res;
}
void solve() {
cin >> m >> n >> K;
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
cin >> a[i][j];
}
}
power[0] = base;
for (int i = 1; i < 31; i++) power[i] = (power[i-1]*power[i-1])%mod;
for (int dir = 0; dir < 8; dir++) {
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
Hash[i][j][0] = a[i][j];
}
}
for (int p = 1; p < 31; p++) {
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
long long u = (i+(1ll << (p-1))*dx[dir]%m+m)%m;
long long v = (j+(1ll << (p-1))*dy[dir]%n+n)%n;
Hash[i][j][p] = (Hash[i][j][p-1]*power[p-1]+Hash[u][v][p-1])%mod;
}
}
}
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
cnt[cal(i,j,dir)]++;
}
}
}
long long y = 1ll*(n*m*8)*(n*m*8);
long long x = 0;
for (auto p:cnt) {
x += 1ll*p.second*p.second;
}
long long d = __gcd(x,y);
x /= d;
y /= d;
cout << x << "/" << y;
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
solve();
}
