View Compilation Error

0_0_31481950_8402.cpp: In function 'int main()':
0_0_31481950_8402.cpp:99:9: error: 'head' was not declared in this scope
         head=0,tail=0;
         ^
0_0_31481950_8402.cpp:99:16: error: 'tail' was not declared in this scope
         head=0,tail=0;
                ^