/in/foo.cc: In function 'll cal(ll, ll, char)':
/in/foo.cc:26:12: warning: 'res' may be used uninitialized in this function [-Wmaybe-uninitialized]
     return res;
            ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:18:8: warning: 'res' may be used uninitialized in this function [-Wmaybe-uninitialized]
     ll res;
        ^~~