蒟蒻求助大佬，为什么只有第二个点TLE？

#include <iostream>

using namespace std;

int n, m;
int a[105][105];
int cnt[105][105];
int xx[5] = {-1, 0, 1, 0};
int yy[5] = {0, -1, 0, 1};
void dfs(int x, int y)
{
     int i, k = 0;
     for (i = 0; i < 4; i++)
       if (a[x + xx[i]][y + yy[i]] <  a[x][y])
       {
           cnt[x + xx[i]][y + yy[i]] = max(cnt[x + xx[i]][y + yy[i]], cnt[x][y] + 1);
           dfs(x + xx[i], y + yy[i]);
       }
       else  k++;
     if (k == 4)  return;
}
int main()
{
    int i, j, maxn = 0;
    cin >> n >> m;
    for (i = 0; i < n; i++)
      for (j = 0; j < m; j++)
      {
          cin >> a[i][j];
          cnt[i][j] = 1;
      }
    for (i = 0; i < n; i++)
      for (j = 0; j < m; j++)
        dfs(i, j);
    for (i = 0; i < n; i++)
      for (j = 0; j < m; j++)
        maxn = max(maxn, cnt[i][j]);
    cout << maxn << endl;
    system("pause");
    return 0;
}