View Compilation Error

0_0_23768973_18101.cpp: In function 'int main()':
0_0_23768973_18101.cpp:58:17: error: 'tag' was not declared in this scope
         if(k>=0)tag=1;//判断y是否大于0
                 ^
0_0_23768973_18101.cpp:64:17: error: 'tag' was not declared in this scope
         if(k>=0)tag=1;
                 ^
0_0_23768973_18101.cpp:65:14: error: 'tag' was not declared in this scope
         puts(tag?"Yes.\n":"No.\n");
              ^