View Compilation Error

0_0_37804689_20428.cpp: In function 'void NTT(long long int*, int, int)':
0_0_37804689_20428.cpp:20:41: error: 'qpow' was not declared in this scope
   ll wn=qpow(op==1?G:invG,(mod-1)/(s<<1));
                                         ^
0_0_37804689_20428.cpp:34:24: error: 'qpow' was not declared in this scope
   ll inv=qpow(len,mod-2);
                        ^
0_0_37804689_20428.cpp: In function 'void init(int)':
0_0_37804689_20428.cpp:46:28: error: 'qpow' was not declared in this scope
     inv[n]=qpow(jc[n],mod-2);
                            ^