View Compilation Error

0_0_39628461_26566.cpp: In function 'int main()':
0_0_39628461_26566.cpp:30:49: error: 'x' was not declared in this scope
   30 |                 for(int i=1;i<=n;i++) stk[i]=ls[x]=rs[x]=0,ans=ans*INV[siz[i]]%mod;
      |                                                 ^