View Compilation Error

0_0_29098611_9495.cpp: In member function 'll Mod::pow(ll, ll) const':
0_0_29098611_9495.cpp:31:47: error: passing 'const Mod' as 'this' argument of 'll Mod::mul(ll, ll)' discards qualifiers [-fpermissive]
   for (a = add(a, 0); b; b >>= 1, a = mul(a, a))
                                               ^
0_0_29098611_9495.cpp:33:17: error: passing 'const Mod' as 'this' argument of 'll Mod::mul(ll, ll)' discards qualifiers [-fpermissive]
     r = mul(r, a);
                 ^