View Compilation Error

0_0_19373031_1415.cpp: In function 'void work(int)':
0_0_19373031_1415.cpp:41:31: error: invalid operands of types '__gnu_cxx::__promote_2<int, int, double, double>::__type {aka double}' and 'long long int' to binary 'operator%'
  ans=(pow(2,n)-1-n-n*(n-1)/2)%mod;
                               ^