#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>

using namespace std;
using namespace __gnu_pbds;

template<typename T>
ostream_iterator<T> oit(const string &s = " "){ return ostream_iterator<T>(cout,s.c_str()); }
inline auto rep(int l, int r) { return views::iota(min(l, r), r); }
inline auto rep(int n) { return rep(0, n); }
inline auto rep1(int l, int r) { return rep(l, r + 1); }
inline auto rep1(int n) { return rep(1, n + 1); }
inline auto per(int l, int r) { return rep(l, r) | views::reverse; }
inline auto per(int n) { return per(0, n); }
inline auto per1(int l, int r) { return per(l, r + 1); }
inline auto per1(int n) { return per(1, n + 1); }
#define A(a) begin(a),end(a)
inline auto len = ranges::ssize;

struct chash {
    static uint64_t splitmix64(uint64_t x) {
        // http://xorshift.di.unimi.it/splitmix64.c
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};
template<typename T, typename U> using pb_map = gp_hash_table<T, U, chash>;
template<typename T> using pb_set = gp_hash_table<T, null_type, chash>;
#define K first
#define V second

using ll = long long;
using ld = long double;

using vi = vector<int>;
using vii = vector<vector<int>>;
typedef vector<ll> vll;
using pll = pair<ll,ll>;
using pii = pair<int,int>;

constexpr ll NN = 2e5, M = 1000000007, L = 20;

ll f1[NN], f2[NN];
ll inv(ll a, ll b=M) { return 1 < a ? b - inv(b % a, a) * b / a : 1; } // inv a mod b
ll choose(ll n, ll k) { return f1[n] * f2[k] % M * f2[n - k] % M; } // n choose k

int dp[52][52][52][52][2];

void run()
{
    memset(dp, 0x3f, sizeof(dp));
    int m, n, k;
    cin>>m>>n>>k;

    vector<string> a(m, string(n, ' '));
    for (auto &x : a) for (auto &x : x) cin >> x;
    vector<string> words(k);
    for (auto &x : words) cin >> x;

    for (int j = 1; j <= n; j++) {
        dp[0][j][0][(int)words[0].size() - 1][0] = 0;
        dp[0][j][0][(int)words[0].size() - 1][1] = 0;
    }

    for (int i = 1; i <= m; i++) {
        for (int j = 1; j <= n; j++) {
            int minw = 1e9;
            for (int w = 0; w < k; w++) {
                int l = words[w].size();
                minw = min({
                    minw,
                    dp[i-1][j][w][l - 1][0],
                    dp[i-1][j][w][l - 1][1],
                    dp[i][j-1][w][l - 1][0]
                });
            }
            for (int w = 0; w < k; w++) {
                if (a[i-1][j-1] == words[w][0])
                    dp[i][j][w][0][0] = minw + 1;
                for (int l = 1; l < (int)words[w].size(); l++) {
                    if (a[i-1][j-1] != words[w][l]) continue;
                    dp[i][j][w][l][0] = min({
                        dp[i-1][j][w][l - 1][0],
                        dp[i-1][j][w][l - 1][1],
                        dp[i][j-1][w][l - 1][0]
                    }) + 1;
                }
            }
        }
        for (int j = n; j >= 1; j--) {
            int minw = 1e9;
            for (int w = 0; w < k; w++) {
                int l = words[w].size();
                minw = min({
                    minw,
                    dp[i-1][j][w][l - 1][0],
                    dp[i-1][j][w][l - 1][1],
                    dp[i][j+1][w][l - 1][1]
                });
            }
            for (int w = 0; w < k; w++) {
                if (a[i-1][j-1] == words[w][0])
                    dp[i][j][w][0][1] = minw + 1;
                for (int l = 1; l < (int)words[w].size(); l++) {
                    if (a[i-1][j-1] != words[w][l]) continue;
                    dp[i][j][w][l][1] = min({
                        dp[i-1][j][w][l - 1][0],
                        dp[i-1][j][w][l - 1][1],
                        dp[i][j+1][w][l - 1][1]
                    }) + 1;
                }
            }
        }
    }
    int ans = 1e9;
    for (int j = 1; j <= n; j++) {
        for (int w = 0; w < k; w++) {
            ans = min({ans, dp[m][j][w][(int)words[w].size()-1][0], dp[m][j][w][(int)words[w].size()-1][1]});
        }
    }
    if (ans >= 1e9)
        cout << "impossible";
    else
    cout << ans;
}

int main()
{
    //KING OF THE WORLD...... U.W.T.B
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    run();
}