#include <cstdio>
#include <iostream>
#include <cstdlib>
#include <algorithm>

#define N 50

using namespace std;

int n, m, a[N][N], answer = 0, res;

void rec(int x, int y) {

    if (res + (n - y) * m + m - x + 1 <= answer)
        return;

    int nx = x + 1, ny = y;
    if (nx == m + 1) {
        nx = 0;
        ny++;
        if (ny == n + 1) {
            answer = max(answer, res);
            return;
        }
    }

    if (a[x][y] == 1) {
        if (x > 1 && a[x - 1][y] > 0) {
            a[x][y]--;
            a[x - 1][y]++;
            res++;
            rec(nx, ny);
            res--;
            a[x][y]++;
            a[x - 1][y]--;
        }

        if (x < m && a[x + 1][y] > 0) {
            a[x][y]--;
            a[x + 1][y]++;
            res++;
            rec(nx, ny);
            res--;
            a[x][y]++;
            a[x + 1][y]--;
        }

        if (y < n && a[x][y + 1] > 0) {
            a[x][y]--;
            a[x][y + 1]++;
            res++;
            rec(nx, ny);
            res--;
            a[x][y]++;
            a[x][y + 1]--;
        }

        if (y > 1 && a[x][y - 1] > 0) {
            a[x][y]--;
            a[x][y - 1]++;
            res++;
            rec(nx, ny);
            res--;
            a[x][y]++;
            a[x][y - 1]--;
        }
    }

    rec(nx, ny);
}

int main() {
    freopen("sol.cpp", "w", stdout);

    for (m = 1; m <= 40; m++)
        for (n = 1; n * m <= 40; n++) {
            for (int i = 1; i <= m; i++)
                for (int j = 1; j <= m; j++)
                    a[i][j] = 1;
            answer = 0, res = 0;
            rec(1, 1);
            printf("a[%d][%d] = %d;\n", m, n, answer);
            cerr << m << " " << n << endl;
    }
    return 0;
}