#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <sstream>
#include <vector>
#include <complex>
#include <ctime>
#include <stack>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> VI;
typedef vector< VI > VVI;
typedef pair<int, int> PII;
typedef vector<PII> VPII;

#define REP(i, n) for(int i = 0; i < n; ++i)
#define RREP(i, n) for(int i = n - 1; i >= 0; --i)
#define FOR(i, x, y) for(int i = x; i <= y; ++i)
#define RFOR(i, x, y) for(int i = x; i >= y; --i)
#define SZ(a) (int)(a).size()
#define ALL(a) (a).begin(),(a).end()
#define SORT(a) sort(ALL(a))
#define CLEAR(x) memset(x, 0, sizeof x);
#define COPY(FROM, TO) memcpy(TO, FROM, sizeof TO);
#define UNIQUE(c) SORT(c),(c).resize(unique(ALL(c))-(c).begin())
#define pb push_back
#define mk make_pair
#define sqr(x) (x)*(x)
#define X first
#define Y second
const long double pi=acos(-1.0);
const long double eps = 1e-6;
const int inf = 1e+9;
const int N = 1e+4;

int n, m, k;
string s1;
string mp[51];
bool dp[50][50];
int sum[51][51];
int query (int x1, int y1, int x2, int y2) {
	if (x1 == 0 && y1 == 2 && x2 == 2 && y2 == 12)
		int r = 2;
	int res = sum[x2][y2];
	if (x1 >= 1)
		res -= sum[x1 - 1][y2];
	if (y1 >= 1)
		res -= sum[x2][y1 - 1];
	if (x1 - 1 >= 0 && y1 - 1 >= 0)
		res += sum[x1 - 1][y1 - 1];
	return res;
}
int main () {
	cin >> n >> m >> k >> s1;
	REP (i, n)
		cin >> mp[i];
	REP (i, n)
		REP (j, m) {
			bool f = 0;
			REP (i1, SZ(s1))
				if (s1[i1] == mp[i][j]) {
					f = 1;
					break;
				}
			if (f)
				dp[i][j] = 1;
		}
	sum[0][0] = dp[0][0];
	FOR (i, 1, n - 1)
		sum[i][0] = sum[i - 1][0] + dp[i][0];
	FOR (j, 1, m - 1)
		sum[0][j] = sum[0][j - 1] + dp[0][j];
	FOR (i, 1, n - 1)
		FOR (j, 1, m - 1)
			sum[i][j] += sum[i][j - 1] + sum[i - 1][j] + dp[i][j] - sum [i - 1][j - 1];
	double maxx = 0;
	int an = 0;
	int sz = -1;
	FOR (i, 0, n - 1)
		FOR (j, 0, m - 1)
			FOR (x, k, n)
				FOR (y, k, m) {
					if (i + x - 1 > n - 1 || j + y - 1> m - 1)
						continue;
					double p = query (i, j, i + x - 1, j + y - 1);
					double t = p / (x * y);
					if (t > maxx) {
						maxx = t;
						an = p;
						sz = x * y;
					} else if (t == maxx && (x * y) > sz) {
						an = p;
						sz = x * y;
					}
				}
	cout << an << "/" << sz;
	return 0;
}
/*
5
-15 -22 21 -211 -2112
*/