include[HTML_REMOVED]

include[HTML_REMOVED]

using namespace std;
const int N = 1e5+10;
int s[26];
int main()
{
int idx=-1;
string a;
cin>>a;
for(int i=0;i<a.size();i)
s[a[i]-‘a’];
for(int i=0;i<a.size();i++)
if(s[a[i]-‘a’]==1)
{
idx=i;
break;
}
if(idx==-1) cout<<”no”;
else cout<<a[idx];
return 0;
}