You are given matrix a of size n × m, its elements are integers. We will assume that the rows of the matrix are numbered from top to bottom from 1 to n, the columns are numbered from left to right from 1 to m. We will denote the element on the intersecting of the i-th row and the j-th column as aij.

We'll call submatrix i1, j1, i2, j2 (1 ≤ i1 ≤ i2 ≤ n; 1 ≤ j1 ≤ j2 ≤ m) such elements aij of the given matrix that i1 ≤ i ≤ i2 AND j1 ≤ j ≤ j2. We'll call the area of the submatrix number (i2 - i1 + 1)·(j2 - j1 + 1). We'll call a submatrix inhomogeneous, if all its elements are distinct.

Find the largest (in area) inhomogenous submatrix of the given matrix.

Input

The first line contains two integers n, m (1 ≤ n, m ≤ 400) — the number of rows and columns of the matrix, correspondingly.

Each of the next n lines contains m integers aij (1 ≤ aij ≤ 160000) — the elements of the matrix.

Output

Print a single integer — the area of the optimal inhomogenous submatrix.

Examples

Input

3 3
1 3 1
4 5 6
2 6 1


Output

6


Input

3 4
5 2 3 1
3 3 5 3
4 4 4 5


Output

4


Input

2 6
1 2 3 4 5 6
8 6 7 8 9 1


Output

8
#include <bits/stdc++.h>
using namespace std;
void RD(int &x) { scanf("%d", &x); }
void RD(long long &x) { scanf("%I64d", &x); }
void RD(unsigned long long &x) { scanf("%I64u", &x); }
void RD(unsigned int &x) { scanf("%u", &x); }
void RD(double &x) { scanf("%lf", &x); }
void RD(int &x, int &y) { scanf("%d%d", &x, &y); }
void RD(long long &x, long long &y) { scanf("%I64d%I64d", &x, &y); }
void RD(unsigned int &x, unsigned int &y) { scanf("%u%u", &x, &y); }
void RD(double &x, double &y) { scanf("%lf%lf", &x, &y); }
void RD(int &x, int &y, int &z) { scanf("%d%d%d", &x, &y, &z); }
void RD(long long &x, long long &y, long long &z) {
  scanf("%I64d%I64d%I64d", &x, &y, &z);
}
void RD(unsigned int &x, unsigned int &y, unsigned int &z) {
  scanf("%u%u%u", &x, &y, &z);
}
void RD(double &x, double &y, double &z) { scanf("%lf%lf%lf", &x, &y, &z); }
void RD(char &x) { x = getchar(); }
void RD(char *s) { scanf("%s", s); }
void RD(string &s) { cin >> s; }
void PR(int x) { printf("%d\n", x); }
void PR(int x, int y) { printf("%d %d\n", x, y); }
void PR(long long x) { printf("%I64d\n", x); }
void PR(unsigned int x) { printf("%u\n", x); }
void PR(unsigned long long x) { printf("%I64u\n", x); }
void PR(double x) { printf("%.9lf\n", x); }
void PR(char x) { printf("%c\n", x); }
void PR(char *x) { printf("%s\n", x); }
void PR(string x) { cout << x << endl; }
void upMax(int &x, int y) {
  if (x < y) x = y;
}
void upMax(long long &x, long long y) {
  if (x < y) x = y;
}
void upMax(double &x, double y) {
  if (x < y) x = y;
}
void upMin(int &x, int y) {
  if (x > y) x = y;
}
void upMin(long long &x, long long y) {
  if (x > y) x = y;
}
void upMin(double &x, double y) {
  if (x > y) x = y;
}
const int mod = 1000000007;
const long long inf = ((long long)1) << 60;
const double dinf = 1e50;
const int INF = 2000000005;
const int N = 405;
int a[N][N], n, m, f[N][N];
map<int, int> mp[N * N];
int main() {
  RD(n, m);
  int i, j, k, t;
  for (i = 0; i < n; i++)
    for (j = 0; j < m; j++) RD(a[i][j]);
  int ans = 0;
  for (i = 0; i < n; i++) {
    for (j = 0; j < m; j++) {
      map<int, int>::iterator it;
      int x = a[i][j];
      for (it = mp[x].begin(); it != mp[x].end(); it++) {
        int a = it->first;
        int b = j;
        if (a > b) swap(a, b);
        upMax(f[a][b], it->second);
      }
      mp[x][j] = i + 1;
    }
    for (t = 1; t < m; t++)
      for (k = 0; k + t < m; k++) {
        upMax(f[k][k + t], f[k][k + t - 1]);
        upMax(f[k][k + t], f[k + 1][k + t]);
      }
    for (t = 0; t < m; t++)
      for (k = t; k < m; k++) {
        upMax(ans, (i - f[t][k] + 1) * (k - t + 1));
      }
  }
  PR(ans);
}
