View Compilation Error

0_0_18815788_25162.cpp: In function 'void init()':
0_0_18815788_25162.cpp:17:5: error: 'vst' was not declared in this scope
     vst.clear();chats.clear();
     ^
0_0_18815788_25162.cpp: In function 'void Add(int, int)':
0_0_18815788_25162.cpp:27:8: error: 'vst' was not declared in this scope
     if(vst[num])    printf("Operation #%d: same priority.\n",cas);
        ^
0_0_18815788_25162.cpp: In function 'void Close(int, int)':
0_0_18815788_25162.cpp:40:9: error: 'vst' was not declared in this scope
     if(!vst[num])   printf("Operation #%d: invalid priority.\n",cas);
         ^
0_0_18815788_25162.cpp: In function 'void final_deal()':
0_0_18815788_25162.cpp:139:5: error: 'vst' was not declared in this scope
     vst[always_top]=0;
     ^