View Compilation Error

1_868_6961_24948.cpp: In function 'int main()':
1_868_6961_24948.cpp:13:2: error: 'in' was not declared in this scope
  in a=(x+y)/2;
  ^
1_868_6961_24948.cpp:14:8: error: 'a' was not declared in this scope
  int b=a-y;
        ^