View Compilation Error

0_0_38424396_24571.cpp: In function 'int bfs(int, int)':
0_0_38424396_24571.cpp:82:87: error: 'num' was not declared in this scope
                 if(dx>=0 && dx<MAX && dy>=0 && dy<MAX && !visited[dx][dy] && !isprime[num]){//判断合法性
                                                                                       ^
0_0_38424396_24571.cpp:83:25: error: redeclaration of 'int num'
                     int num=grind[dx][dy];
                         ^
0_0_38424396_24571.cpp:82:87: note: '<typeprefixerror>num' previously declared here
                 if(dx>=0 && dx<MAX && dy>=0 && dy<MAX && !visited[dx][dy] && !isprime[num]){//判断合法性
                                                                                       ^