# include<iostream> # include<cstring> using namespace std; string a; int b[128]; int main(){ cin>>a; for(int i=0;i<a.size();i++) b[a[i]]++; for(int i=0;i<a.size();i++){ if(b[a[i]]==1){ cout<<a[i]; return 0; } } cout<<"no"; return 0; }