我只做到，換成數值並算出答案那邊。只是算出來的答案是錯的，有沒有人可以教教我??

#include<iostream>
#include<cstring>
#include<cmath>
using namespace std;
int num(char x)
{
    int b;
             switch(x)
             {
              case 'I':
              b=1;
              break;
              case 'V':
              b=5;
              break;
              case 'X':
              b=10;
              break;
              case 'L':
              b=50;
              break;
              case 'C' :
              b=100;
              break;
              case 'D' :
              b=500;
              break;
              case 'M' :
              b=1000;
              break;
              }
              return b;
}
main()
{
     
      string a,b;
      while(cin>>a)
      {
                   int c=0,d=0,e;
                   if(a=="#")break;
                    cin>>b;
                    if(a==b)
                    {
                            cout<<"ZERO";
                            }
                    else
                    {
                   for(int i=1;i<=a.length();i++)
                   {
                           c +=num(a[i]);
                           
                   }
                   for(int y=1;y<=b.length();y++)
                   {
                           d+= num(b[y]);
                         
                   }
                   e=abs(c-d);
                   cout<<e;
                   }
      }
      return 0;
}