View Compilation Error

0_0_32597750_27450.cpp: In function 'int main()':
0_0_32597750_27450.cpp:47:54: error: lvalue required as increment operand
   for(i=1;i<=n;i++)scanf("%d",&aa[i]),f[aa[i]].real()++;
                                                      ^
0_0_32597750_27450.cpp:55:37: error: lvalue required as left operand of assignment
   for(i=1;i<=n;i++)f[aa[i]*2].real()-=1;
                                     ^