wa*2求助

#include<iostream>
#include<cmath>
using namespace std;
int n, m, a[105][105], b[105][105],f[105][105], i, j, ans;
int dfs(int x, int y)
{
    int mmax = -1;
    if (f[x][y])
        return b[x][y];
    else {
        if (a[x + 1][y] != 0 && a[x + 1][y] < a[x][y] && x + 1 != n + 1)
            mmax=max( dfs(x + 1, y) + 1, mmax);
        if (a[x - 1][y] != 0 && a[x - 1][y] < a[x][y] && x - 1 != n + 1)
            mmax = max(dfs(x - 1, y) + 1, mmax);
        if (a[x][y + 1] != 0 && a[x][y + 1] < a[x][y] && y + 1 != m + 1)
            mmax = max(dfs(x, y + 1) + 1, mmax);
        if (a[x][y - 1] != 0 && a[x][y - 1] < a[x][y] && y - 1 != m + 1)
            mmax = max(dfs(x, y - 1) + 1, mmax);
        if (mmax == -1)
            mmax = 1;
        b[x][y] = mmax;
        f[x][y] = 1;
        return b[x][y];
    }
}
int main() {
    cin >> n >> m;
    for (i = 1; i <= n; i++)
    {
        for (j = 1; j <= m; j++)
        {
            cin >> a[i][j];
        }
    }
    for (i = 1; i <= n; i++)
    {
        for (j = 1; j <= m; j++)
        {
            ans = max(dfs(i,j), ans);
        }
    }
    cout << ans;
    return 0;
}

第五个点和第七个点wa了。。。。