foo.cc: In function 'void solve()':
foo.cc:93:12: error: conflicting declaration 'double res'
   93 |     double res = 3.141592653589793 * 2 * r;
      |            ^~~
foo.cc:74:12: note: previous declaration as 'std::string res'
   74 |     string res = to_string(a) + ", " + to_string(b) + ", " + to_string(r) + ": ";
      |            ^~~