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