View Compilation Error

0_0_32343692_191.cpp: In function 'int main()':
0_0_32343692_191.cpp:21:16: error: 'i' was not declared in this scope
   ans=ans^(2*a[i]);
                ^
0_0_32343692_191.cpp:25:18: error: 'ans' was not declared in this scope
  printf("%lld\n",ans);
                  ^