我只輸出一次，他卻輸出好幾次

#include<iostream>
using namespace std;
main()
{
      char s;
      int i,r;
      while (cin>>s))
      {
            r=0;
            for (i=0;i<strlen(s);i++)
            {
                if  ((s[i]>90&&s[i]<65)||(s[i]>122&&s[i]<97))
                {
                    r++;
                }
            }
            cout<<r<<"\n";
      }
}