View Compilation Error

0_0_26053626_17448.cpp: In function 'll sum(ll)':
0_0_26053626_17448.cpp:30:30: error: invalid operands of types '__gnu_cxx::__promote_2<int, long long int, double, double>::__type {aka double}' and 'const ll {aka const long long int}' to binary 'operator%'
  ret = (ret * pow(3,mod-2)) %mod;
                              ^