icpc2017_C.cpp

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cmath>

using namespace std;
using ll = long long;
#define rep(i,n) for(int i=0;i<(n);i++)
#define out(S) cout<<(S)<<endl;

int H, W;
int area[11][11];

int min_out(int y, int x, int h, int w) {
	int ret = 1000;
	rep(i, H) rep(j, W) {
		if (y <= i && i <= y + h - 1 && x <= j && j <= x + w - 1) {
			if (i == y) ret = min(ret, area[i][j]);
			if (j == x) ret = min(ret, area[i][j]);
			if (i == y + h - 1) ret = min(ret, area[i][j]);
			if (j == x + w - 1) ret = min(ret, area[i][j]);
		}
	}

	return ret;
}

int max_in(int y, int x, int h, int w) {
	int ret = 0;
	rep(i, H) rep(j, W) {
		if (y < i && i < y + h - 1 && x < j && j < x + w - 1) {
			// cout << "in = " << i << ", " << j << endl;
			ret = max(ret, area[i][j]);
		}
	}

	return ret;
}

int sum_in(int y, int x, int h, int w) {
	int ret = 0;
	rep(i, H) rep(j, W) {
		if (y < i && i < y + h - 1 && x < j && j < x + w - 1) {
			// cout << "in = " << i << ", " << j << endl;
			ret += area[i][j];
		}
	}

	return ret;
}

void solve() {
	// cout << min_out(0, 1, 3, 5) << endl;
	// cout << max_in(0, 1, 3, 5) << endl;
	int ans = 0;
	rep(y, H) rep(x, W) rep(h, H + 1) rep(w, W + 1) {
		if (h < 3) continue;
		if (w < 3) continue;
		if (y + h - 1 >= H) continue;
		if (x + w - 1 >= W) continue;
		int a = min_out(y, x, h, w);
		int b = max_in(y, x, h, w);
		if (b >= a) continue;
		int s = sum_in(y, x, h, w);
		int c = a * (h - 2) * (w - 2);
		// printf("%d %d %d %d = %d %d %d %d: %d\n", y, x, h, w, a, b, s, c, c - s);
		ans = max(ans, c - s);
	}

	cout << ans << endl;
}

int main() {
	while (cin >> H >> W, H) {
		rep(i, H) rep(j, W) cin >> area[i][j];
		solve();
	}

	return 0;
}