View Compilation Error

0_0_19270549_16986.cpp: In function 'int main()':
0_0_19270549_16986.cpp:44:39: error: lvalue required as left operand of assignment
   for (int i=0;i<n;++i) a[o[i]].real()=a[o[i]].real()+1,mx=max(mx,o[i]);
                                       ^