View Compilation Error

0_0_25572272_23245.cpp: In function 'int main()':
0_0_25572272_23245.cpp:68:59: error: invalid initialization of non-const reference of type 'LL& {aka long long int&}' from an rvalue of type 'LL {aka long long int}'
                 add(sum[nxt][nid], sum[now][id]*v[g[k][z]]%mod);
                                                           ^
0_0_25572272_23245.cpp:30:4: note: in passing argument 2 of 'LL add(LL&, LL&)'
 LL add(LL& x, LL &y){
    ^