#include <bits/stdc++.h>
using namespace std;
template <typename A, typename B>
string to_string(pair<A, B> p);
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);
string to_string(const string& s) { return '"' + s + '"'; }
string to_string(const char* s) { return to_string((string)s); }
string to_string(bool b) { return (b ? "true" : "false"); }
string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}
template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}
template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto& x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ")";
}
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
const int mod = 1e9 + 7;
const int inf = 1 << 30;
const int maxn = 505;
int n, m, k;
int cuantas[maxn], tomar[maxn][maxn], dp[maxn][maxn];
vector<int> pos[maxn];
int solve(int i, int f) {
  if (f > k) return inf;
  if (i > n) return 0;
  int& res = dp[i][f];
  if (res != -1) return res;
  res = inf;
  for (int j = 0; j <= cuantas[i]; j++) {
    int faltar = cuantas[i] - j;
    if (f + faltar <= k) {
      res = min(res, solve(i + 1, f + faltar) + tomar[i][j]);
    }
  }
  return res;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cin >> n >> m >> k;
  for (int i = 1; i <= n; i++) {
    string s;
    cin >> s;
    for (int j = 0; j < m; j++) {
      if (s[j] == '0') continue;
      pos[i].push_back(j);
    }
    cuantas[i] = (int)pos[i].size();
  }
  for (int i = 1; i <= n; i++) {
    for (int tam = 1; tam <= cuantas[i]; tam++) {
      tomar[i][tam] = inf;
      for (int j = 0; j < cuantas[i]; j++) {
        if (j + tam - 1 >= cuantas[i]) break;
        tomar[i][tam] = min(tomar[i][tam], pos[i][j + tam - 1] - pos[i][j] + 1);
      }
    }
  }
  memset(dp, -1, sizeof(dp));
  cout << solve(1, 0) << '\n';
  return 0;
}
