foo.cc: In function 'int main()':
foo.cc:9:39: error: lvalue required as left operand of assignment
   if(c[i]-0 >=95) (char)c[i] = c[i] - 'A';
                                       ^~~
foo.cc:12:39: error: lvalue required as left operand of assignment
   if(k[i]-0 >=95) (char)k[i] = k[i] - 'A';
                                       ^~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。