幫忙看一下好嗎??

#include<iostream>
using namespace std;
int main()
{    
    string a;
    while(getline(cin,a))
    {         
        int b=a.size();
        int d;
        for(int i=0;i<b;i+=2)
        {
            d=1;
            if(a[i]!='0')
            {
                for(int j=i+2;j<b;j+=2)
                {
                    if(a[i]==a[j])
                    {
                        d++;
                        a[j]='0';
                    }
                }
                if(d%3!=0)
                {
                   cout << a[i];
                   break;
                }
            }
        }
        cout << endl;
    }
    return EXIT_SUCCESS;
}

好吧

我突然想到我問題在哪了= =

範例給的都是個位數字的輸入

害我有點誤會了= =