View Compilation Error

0_0_21601074_11355.cpp:18:30: error: stray '#' in program
             ans=pre*10+a[i]-'0';
                              ^
0_0_21601074_11355.cpp:18:36: error: stray '#' in program
             ans=pre*10+a[i]-'0';
                                    ^
0_0_21601074_11355.cpp: In function 'int main()':
0_0_21601074_11355.cpp:18:31: error: lvalue required as unary '&' operand
             ans=pre*10+a[i]-'0';
                               ^