View Compilation Error

0_0_21505874_24959.cpp: In function 'void work()':
0_0_21505874_24959.cpp:210:21: error: 'num' was not declared in this scope
         for (auto i:num[b[j]]) {
                     ^
0_0_21505874_24959.cpp:217:21: error: 'num' was not declared in this scope
         for (auto i:num[b[j]]) {
                     ^