#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <iostream>
#include <istream>
#include <iterator>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#include <tuple>
#include <iomanip>
#include <climits>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
//typedef pair<ll, ll> P;
#define rep(i, n) for(int i = 0; i < (n); i++)
#define revrep(i, n) for(int i = (n)-1; i >= 0; i--)
#define pb push_back
#define f first
#define s second
#define chmin(x, y) x = min(x, y);
#define chmax(x, y) x = max(x, y);

//const ll INFL = LLONG_MAX;//10^18 = 2^60
const ll INFL = 1LL<<60;
//const int INF = INT_MAX;
const ll INF = 1 << 30;//10^9
ll MOD = 1000000007;
//ll MOD = 998244353;

vector<ll> dy = {0, 1, 0, -1, 1, 1, -1, -1, 0};
vector<ll> dx = {1, 0, -1, 0, 1, -1, 1, -1, 0};

void pres(double A){printf("%.9lf\n", A);}
void BinarySay(ll x, ll y = 60){rep(i, y) cout << (x>>(y-1-i) & 1); cout << endl;}
ll cnt_bit(ll x){return __builtin_popcountll(x);}

ll pow_long(ll x, ll k){
  ll res = 1;
  while(k > 0){
    if(k % 2) res *= x;
    x *= x; k /= 2;
  }
  return res;
}

ll pow_mod(ll x, ll k){
  ll res = 1;
  while(k > 0){
    if(k % 2){
      res *= x; res %= MOD;
    }
    x *= x; x %= MOD;
    k /= 2;
  }
  return res;
}

ll inverse(ll x){return pow_mod(x, MOD - 2);};

ll gcd(ll a, ll b){
    if(b == 0) return a;
    return gcd(b, a % b);
}

ll lcm(ll x, ll y){
  ll res = x / gcd(x, y);
  res *= y;
  return res;
};


//コンビネーション
const int MAXcomb = 2000010;
ll fac[MAXcomb], finv[MAXcomb], inv[MAXcomb];
//facはn!,finvは1/n!
//invは逆元
void COMinit(){
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for(int i = 2; i < MAXcomb; i++){
        fac[i] = fac[i-1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD/i) % MOD;
        finv[i] = finv[i-1] * inv[i] % MOD;
    }
}
ll comb(int n, int k){
    if(n < k) return 0;
    if(n < 0 || k < 0) return 0;
    return fac[n] * finv[k] % MOD * finv[n-k] % MOD;
}

const int MAXkai = 200010;
ll kai_memo[MAXkai];
ll kai(ll N){
  if(kai_memo[N] != 0) return kai_memo[N];
  if(N <= 1) return 1;
  return kai_memo[N] = N * kai(N-1) % MOD;
}

ll disit(ll s, ll base = 10){
  ll res = 0;
  while(s){
    res++;
    s /= base;
  }
  return res;
}


int H, W, K;
int c[31][31];
int tmp[31][31];

int add(){
  for(int j = 0; j < W; j++){
    for(int i = H - 1; i >= 0; i--){
      bool update = 1;
      while(update){
        update = 0;
        if(tmp[i][j]) break;
        for(int k = i; k >= 1; k--){
          if(tmp[k][j] != tmp[k-1][j]) update = 1;
          tmp[k][j] = tmp[k-1][j];
        }
        tmp[0][j] = 0;
        if(!update) break;
      }
    }
  }

  int res = 0;
  for(int i = 0; i < H; i++){
    int num = -1, len = 0;
    for(int j = 0; j < W + 1; j++){
      if(tmp[i][j] != num){
        if(len >= K){
          for(int k = j - len; k < j; k++){
            res += tmp[i][k];
            tmp[i][k] = 0;
          }
        }
        num = tmp[i][j];
        len = 1;
      }else{
        len++;
      }
    }
  }
  return res;
}

int calc(int ei, int ej){
  rep(i, H)rep(j, W) tmp[i][j] = c[i][j];
  tmp[ei][ej] = 0;
  int ans = 0;
  for(int i = 0;; i++){
    int res = add();
    if(res == 0) break;
    ans += (1<<i) * res;
  }
  return ans;
}

void solve(){
  cin >> H >> W >> K;
  rep(i, H){
    string S;
    cin >> S;
    rep(j, W) c[i][j] = S[j] - '0';
  }
  int ans = 0;
  rep(i, H)rep(j, W){
    ans = max(ans, calc(i, j));
  }
  cout << ans << endl;
}


int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  solve();
}


Measured memory_bytes: 256