#include <bits/stdc++.h>
using namespace std;

#define fs first
#define sc second
#define pb emplace_back
#define mp make_pair
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()

const int32_t inf = 1001001001;
const int64_t infll = 1001001001001001001ll;
const int dx[] = {0, -1, 1, 0, -1, 1, -1, 1}, dy[] = {-1, 0, 0, 1, -1, -1, 1, 1};

template <typename T> using vector2d = vector<vector<T>>;

// clang-format off
template <typename T> void sort(vector<T> &v) { sort(all(v)); }
// ostream &operator<<(ostream &os, __int128_t value) { if (ostream::sentry(os)) { __uint128_t tmp = value < 0 ? -value : value; char buffer[64]; char *d = end(buffer); do { --d; *d = "0123456789"[tmp % 10]; tmp /= 10; } while (tmp != 0); if (value < 0) { --d; *d = '-'; } int len = end(buffer) - d; if (os.rdbuf()->sputn(d, len) != len) { os.setstate(ios_base::badbit); }} return os; }
// istream &operator>>(istream &is, __int128_t &value) { string in; is >> in; value = 0; for (const char &c : in) { if ('0' <= c && c <= '9') value = 10 * value + (c - '0'); } if (in[0] == '-') value *= -1; return is; }
// ostream &operator<<(ostream &os, __uint128_t value) { if (ostream::sentry(os)) { char buffer[64]; char *d = end(buffer); do { --d; *d = "0123456789"[value % 10]; value /= 10; } while (value != 0); int len = end(buffer) - d; if (os.rdbuf()->sputn(d, len) != len) { os.setstate(ios_base::badbit); }} return os; }
// istream &operator>>(istream &is, __uint128_t &value) { string in; is >> in; value = 0; for (const char &c : in) { if ('0' <= c && c <= '9') value = 10 * value + (c - '0'); } return is; }
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) { os << v[0]; for (int i = 1; i < v.size(); ++i) os << " " << v[i]; return os; }
template <typename T> istream &operator>>(istream &is, vector<T> &v) { for (T &in : v) is >> in; return is; }
template <typename T1, typename T2> ostream &operator<<(ostream &os, pair<T1, T2> p) { os << p.fs << " " << p.sc; return os; }
template <typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p) { is >> p.fs >> p.sc; return is; }

// struct IoSetup { IoSetup(){ cin.tie(0); ios::sync_with_stdio(0); cout << fixed << setprecision(10); cerr << fixed << setprecision(10); } } iosetup;

inline int64_t in() { int64_t x = 0; cin >> x; return x; }
template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }
// clang-format on

signed main(int argc, char *argv[]) {
  int h = in(), w = in(), k = in();
  vector2d<int> c(h, vector<int>(w));
  for (int i = h - 1; i >= 0; --i) {
    for (int j = 0; j < w; ++j) {
      scanf("%1d", &c[i][j]);
    }
  }

  int64_t ans = 0;
  // kimeuchi
  for (int y = 0; y < h; ++y) {
    for (int x = 0; x < w; ++x) {
      int score = 0;
      vector2d<int> C = c;
      C[y][x] = -1;

      // cerr << "begin (" << x << ", " << y << ")" << endl;
      for (int co = 1;; co *= 2) {

        // fall
        // cerr << "fall start" << endl;
        // for (int i = h - 1; i >= 0; --i) {
        //   for (int j = 0; j < w; ++j) {
        //     printf("%2d ", C[i][j]);
        //   }
        //   puts("");
        // }
        // puts("");
        for (int j = 0; j < w; ++j) {
          int now = 0;
          for (int i = 0; i < h; ++i) {
            if (C[i][j] != -1) {
              C[now][j] = C[i][j];
              now++;
            }
          }
          for (int i = now; i < h; ++i) {
            C[i][j] = -1;
          }
        }
        // cerr << "fall end" << endl;
        //
        // for (int i = h - 1; i >= 0; --i) {
        //   for (int j = 0; j < w; ++j) {
        //     printf("%2d ", C[i][j]);
        //   }
        //   puts("");
        // }
        // puts("");

        // erase
        // cerr << "erase start" << endl;
        int sum = 0;
        for (int i = 0; i < h; ++i) {
          for (int j = 0; j < w; ++j) {
            if (C[i][j] == -1) continue;

            int cnt = 0;
            for (int l = j; l < w; ++l) {
              if (C[i][j] != C[i][l]) break;
              cnt++;
            }

            if (cnt >= k) {
              for (int l = 0; l < cnt; ++l) {
                sum += C[i][l + j];
                C[i][l + j] = -1;
              }
            }
          }
        }

        // cerr << "erase end" << endl;
        //
        // cerr << "sum = " << sum << endl;
        // for (int i = h - 1; i >= 0; --i) {
        //   for (int j = 0; j < w; ++j) {
        //     printf("%2d ", C[i][j]);
        //   }
        //   puts("");
        // }
        // puts("");

        score += co * sum;
        if (sum == 0) break;
      }

      // printf("(%d, %d) = %d\n", x, y, score);
      chmax(ans, score);
    }
  }

  cout << ans << endl;
}


Measured memory_bytes: 256