View Compilation Error

0_0_37709874_14776.cpp:5:12: error: unable to find numeric literal operator 'operator""a'
 bool check[20a][20];
            ^
0_0_37709874_14776.cpp:5:12: note: use -std=gnu++11 or -fext-numeric-literals to enable more built-in suffixes
0_0_37709874_14776.cpp: In function 'void bfs(int, int, int)':
0_0_37709874_14776.cpp:30:6: error: 'check' was not declared in this scope
   if(check[temp.nowx][temp.nowy]) continue;
      ^
0_0_37709874_14776.cpp:31:3: error: 'check' was not declared in this scope
   check[temp.nowx][temp.nowy]=true;
   ^
0_0_37709874_14776.cpp: In function 'int main()':
0_0_37709874_14776.cpp:57:11: error: 'check' was not declared in this scope
    memset(check,0,sizeof(check));
           ^