#include <bits/stdc++.h>
using namespace std;
template <typename T1, typename T2>
inline void chkmin(T1 &x, T2 y) {
  if (x > y) x = y;
}
template <typename T1, typename T2>
inline void chkmax(T1 &x, T2 y) {
  if (x < y) x = y;
}
inline int readChar();
template <class T = int>
inline T readInt();
template <class T>
inline void writeInt(T x, char end = 0);
inline void writeChar(int x);
inline void writeWord(const char *s);
static const int buf_size = 4096;
inline int getChar() {
  static char buf[buf_size];
  static int len = 0, pos = 0;
  if (pos == len) {
    pos = 0, len = fread(buf, 1, buf_size, stdin);
  }
  if (pos == len) {
    return -1;
  }
  return buf[pos++];
}
inline int readChar() {
  int c = getChar();
  while (c <= 32) {
    c = getChar();
  }
  return c;
}
template <class T>
inline T readInt() {
  int s = 1, c = readChar();
  T x = 0;
  if (c == '-') s = -1, c = getChar();
  while ('0' <= c && c <= '9') x = x * 10 + c - '0', c = getChar();
  return s == 1 ? x : -x;
}
static int write_pos = 0;
static char write_buf[buf_size];
inline void writeChar(int x) {
  if (write_pos == buf_size)
    fwrite(write_buf, 1, buf_size, stdout), write_pos = 0;
  write_buf[write_pos++] = x;
}
template <class T>
inline void writeInt(T x, char end) {
  if (x < 0) writeChar('-'), x = -x;
  char s[24];
  int n = 0;
  while (x || !n) s[n++] = '0' + x % 10, x /= 10;
  while (n--) writeChar(s[n]);
  if (end) writeChar(end);
}
inline void writeWord(const char *s) {
  while (*s) writeChar(*s++);
}
struct Flusher {
  ~Flusher() {
    if (write_pos) fwrite(write_buf, 1, write_pos, stdout), write_pos = 0;
  }
} flusher;
using namespace std;
const int MAXN = 100011;
const int INF = 1000000001;
char s[20][MAXN];
int n, m;
int dp[21 * MAXN][21];
inline void add(int x) {
  int now = 0;
  int cnt = __builtin_popcount(x);
  for (int i = 0; i < n; i++) {
    dp[now][cnt]++;
    if ((x >> i) & 1) {
      now <<= 1;
      now += 2;
    } else {
      now <<= 1;
      now++;
    }
  }
  dp[now][cnt]++;
}
void change(int now, int h, int dist) {
  if (h != dist) {
    change((now << 1) + 1, h + 1, dist);
    change((now << 1) + 2, h + 1, dist);
    for (int i = 0; i <= n; i++) {
      dp[now][i] = dp[(now << 1) + 1][i] + dp[(now << 1) + 2][i];
    }
  } else {
    dp[now][0] = dp[(now << 1) + 2][1];
    dp[now][n] = dp[(now << 1) + 1][n - 1];
    for (int i = 1; i < n; i++) {
      dp[now][i] = dp[(now << 1) + 1][i - 1] + dp[(now << 1) + 2][i + 1];
    }
  }
}
int main() {
  n = readInt(), m = readInt();
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      s[i][j] = readChar();
    }
  }
  for (int i = 0; i < m; i++) {
    int x = 0;
    for (int j = 0; j < n; j++) {
      x <<= 1;
      x += s[j][i] - '0';
    }
    add(x);
  }
  int ans = n * m;
  for (int i = 0; i < (1 << n); i++) {
    int sum = 0;
    for (int j = 0; j <= n; j++) {
      sum += dp[0][j] * min(j, n - j);
    }
    chkmin(ans, sum);
    if (i + 1 != (1 << n)) {
      for (int j = 0; j < n; j++) {
        if (((i >> j) & 1) == 0) {
          change(0, 0, j);
          break;
        }
      }
    }
  }
  writeInt(ans, '\n');
  return 0;
}
