View Compilation Error

0_0_34671199_9423.cpp: In function 'int main()':
0_0_34671199_9423.cpp:17:30: error: a function-definition is not allowed here before '{' token
   bool my_greatr(int i,int j){
                              ^
0_0_34671199_9423.cpp:20:26: error: 'compare' was not declared in this scope
   sort(a.begin(),a.end(),compare);
                          ^