foo.cpp: In function 'int main()':
foo.cpp:27:25: error: cannot convert 'std::string {aka std::basic_string<char>}' to 'char' in assignment
  for(i=n;i>0;i--) ins[i]=ins;
                         ^
foo.cpp: In function 'int work(int)':
foo.cpp:11:2: warning: control reaches end of non-void function [-Wreturn-type]
  }
  ^