1 #include <cstdio>
  2 #include <cstring>
  3 #include <cmath>
  4 #include <algorithm>
  5 #include <queue>
  6 using namespace std;
  7
  8 const int N = 1010;
  9
 10 struct Node
 11 {
 12     int x, y;
 13 };
 14
 15 int dir[4][2] = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
 16 int sxy[N*N];
 17 char mp[N][N];
 18 bool vis[N][N];
 19 int n, m, t, rt, k;
 20 queue<Node> q0;
 21
 22 int bfs0()
 23 {
 24     Node p, ps;
 25     p.x = p.y = 0;
 26     vis[0][0] = 1;
 27     if(mp[0][0] == '0') q0.push(p);
 28     else
 29     {
 30         sxy[0] = 0;
 31         k = 1;
 32         printf("1");
 33         return 0;
 34     }
 35     k = 0;
 36     while(!q0.empty())
 37     {
 38         p = q0.front();
 39         q0.pop();
 40         sxy[k++] = p.x+p.y;
 41         if(p.x == n-1 && p.y == m-1) return 1;
 42         for(int i = 0; i < 4; i++)
 43         {
 44             int sx = p.x+dir[i][0];
 45             int sy = p.y+dir[i][1];
 46             if(sx >= 0 && sx < n && sy >= 0 && sy < m && !vis[sx][sy] && mp[sx][sy] == '0')
 47             {
 48                 vis[sx][sy] = 1;
 49                 ps.x = sx;
 50                 ps.y = sy;
 51                 q0.push(ps);
 52             }
 53         }
 54     }
 55     return 0;
 56 }
 57
 58 void sroot()
 59 {
 60     rt = 0;
 61     for(int i = 0; i < k; i++) if(rt < sxy[i]) rt = sxy[i];
 62 }
 63
 64 void getans()
 65 {
 66     for(int i = rt+1; i <= m+n-2; i++)
 67     {
 68         k = 0;
 69         if(i >= n-1) k = i-n+1;
 70         int tmp = 2;
 71         for(int j = k; j < m && j <= i; j++)
 72         {
 73             if((i-j-1 >= 0 && i-j < n && j >= 0 && vis[i-j-1][j])
 74                || (i-j >= 0 && i-j < n && j-1 >= 0 && vis[i-j][j-1]))
 75             {
 76                 int mid = mp[i-j][j]-'0';
 77                 tmp = tmp < mid ? tmp : mid;
 78             }
 79         }
 80         printf("%d", tmp);
 81         for(int j = k; j < m && j <= i; j++)
 82         {
 83             if((i-j-1 >= 0 && i-j < n && j >= 0 && vis[i-j-1][j])
 84                || (i-j >= 0 && i-j < n && j-1 >= 0 && vis[i-j][j-1]))
 85             {
 86                 if(mp[i-j][j]-'0' == tmp) vis[i-j][j] = 1;
 87             }
 88         }
 89     }
 90     printf("\n");
 91 }
 92
 93 void init()
 94 {
 95     scanf("%d%d", &n, &m);
 96     for(int i = 0; i < n; i++) scanf("%s", mp[i]);
 97     memset(vis, 0, sizeof(vis));
 98     while(!q0.empty()) q0.pop();
 99 }
100
101 int main()
102 {
103     //freopen("test.in", "r", stdin);
104     //freopen("test.out", "w", stdout);
105     scanf("%d", &t);
106     while(t--)
107     {
108         init();
109         if(bfs0()) printf("0\n");
110         else
111         {
112             sroot();
113             getans();
114         }
115     }
116     return 0;
117 }