#include <bits/stdc++.h>
using namespace std;
int t = 1000001;
class myData {
 public:
  int t;
  int x;
  int y;
  int d;
  myData(int t, int x, int y, int d) : t(t), x(x), y(y), d(d) {}
  bool operator<(const myData &a) const { return (this->t < a.t); }
};
long long exponentMod(long long A, long long B, long long C) {
  if (A == 0) return 0;
  if (B == 0) return 1;
  long long y;
  if (B % 2 == 0) {
    y = exponentMod(A, B / 2, C);
    y = (y * y) % C;
  } else {
    y = A % C;
    y = (y * exponentMod(A, B - 1, C) % C) % C;
  }
  return (long long)((y + C) % C);
}
pair<int, int> factorize(long long n) {
  int ans = 1;
  int c = 0;
  for (long long i = 2; i * i <= n; ++i) {
    while (n % i == 0) {
      if (i != 2) ans *= i, c++;
      n /= i;
    }
  }
  if (n != 1) {
    if (n != 2) ans *= n, c++;
  }
  return {ans, c};
}
map<long long, long long> bit;
int N1 = 2e5;
void update(long long i) {
  for (; i <= N1; i += i & (-i)) bit[i]++;
}
long long get(long long i) {
  long long ans = 0;
  for (; i > 0; i -= i & (-i)) ans += bit[i];
  return ans;
}
int now;
bool sortByVal(const myData &a, const myData &b) { return (a.t < b.t); }
long long ans1 = 0;
int spf[1000003];
long long calc[1000003 + 1];
long long nCk(long long n, long long k, long long mod) {
  return ((((calc[n] % mod) * exponentMod(calc[k], mod - 2, mod)) % mod) *
          exponentMod(calc[n - k], mod - 2, mod)) %
         mod;
}
void sieve() {
  spf[1] = 1;
  for (int i = 2; i < 1000003; i++) spf[i] = i;
  for (int i = 4; i < 1000003; i += 2) spf[i] = 2;
  for (int i = 3; i * i < 1000003; i++) {
    if (spf[i] == i) {
      for (int j = i * i; j < 1000003; j += i)
        if (spf[j] == j) spf[j] = i;
    }
  }
}
set<int> getFactorization(int x) {
  set<int> ret;
  while (x != 1) {
    ret.insert(spf[x]);
    x = x / spf[x];
  }
  return ret;
}
bool prime[1000003 + 1];
void sieve2() {
  memset(prime, true, sizeof(prime));
  for (int p = 2; p * p <= 1000003; p++) {
    if (prime[p] == true) {
      for (int i = p * p; i <= 1000003; i += p) prime[i] = false;
    }
  }
}
int MEX(int a[], int n) {
  set<int> s;
  for (int i = 0; i < n; i++) {
    s.insert(a[i]);
  }
  int c = 0;
  for (auto i = s.begin(); i != s.end(); i++) {
    if (*i == c) {
      c++;
    } else
      break;
  }
  return c;
}
int smallestDivisor(int n) {
  if (n % 2 == 0) return 2;
  for (int i = 3; i * i <= n; i += 2) {
    if (n % i == 0) return i;
  }
  return n;
}
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0);
  int n, m, k, i, j, l;
  char s[505];
  int c[505], q[505], dp[505][505];
  cin >> n >> m >> k;
  for (i = 1; i <= n; i++) {
    cin >> s;
    int len = 0;
    for (j = 0; j < m; j++)
      if (s[j] == '1') c[++len] = j;
    for (l = 1; l <= len; l++) {
      q[l] = m;
      for (j = 1; j <= len - l + 1; j++)
        q[l] = min(q[l], c[j + l - 1] - c[j] + 1);
    }
    for (j = 0; j <= k; j++)
      for (l = min(len, j), dp[i][j] = i * m; l >= 0; l--)
        dp[i][j] = min(dp[i][j], dp[i - 1][j - l] + q[len - l]);
  }
  cout << dp[n][k];
  return 0;
}
