View Compilation Error

0_0_30348792_13460.cpp: In instantiation of 'T remainder(const T&) [with T = long long int]':
0_0_30348792_13460.cpp:664:77:   required from here
0_0_30348792_13460.cpp:616:4: error: assignment of read-only reference 'x'
  x %= mod;
    ^
0_0_30348792_13460.cpp: In instantiation of 'T remainder(const T&) [with T = int]':
0_0_30348792_13460.cpp:669:44:   required from here
0_0_30348792_13460.cpp:616:4: error: assignment of read-only reference 'x'