View Compilation Error

0_0_22226058_23731.cpp: In function 'bool ck(int, int, int)':
0_0_22226058_23731.cpp:15:42: error: 'vis' was not declared in this scope
     if(x>=0&&x<n&&y>=0&&y<n&&z>=0&&z<n&&!vis[z][x][y]&&map[z][x][y]=='O')
                                          ^
0_0_22226058_23731.cpp: In function 'void bfs()':
0_0_22226058_23731.cpp:30:12: error: 'vis' was not declared in this scope
     memset(vis,0,sizeof vis);
            ^