foo.cc: In function 'int cal(int, int, int, int, std::__cxx11::string*)':
foo.cc:8:6: warning: unused variable 'sum' [-Wunused-variable]
  int sum = 0;
      ^~~
foo.cc: At global scope:
foo.cc:53:11: error: '::main' must return 'int'
 void main()
           ^
foo.cc: In function 'int main()':
foo.cc:64:3: error: return-statement with no value, in function returning 'int' [-fpermissive]
   return;
   ^~~~~~
foo.cc:67:3: error: return-statement with no value, in function returning 'int' [-fpermissive]
   return;
   ^~~~~~
foo.cc:70:3: error: return-statement with no value, in function returning 'int' [-fpermissive]
   return;
   ^~~~~~
foo.cc:73:3: error: return-statement with no value, in function returning 'int' [-fpermissive]
   return;
   ^~~~~~
foo.cc:76:3: error: return-statement with no value, in function returning 'int' [-fpermissive]
   return;
   ^~~~~~
foo.cc:79:3: error: return-statement with no value, in function returning 'int' [-fpermissive]
   return;
   ^~~~~~
foo.cc: In function 'int cal(int, int, int, int, std::__cxx11::string*)':
foo.cc:51:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^