include[HTML_REMOVED]

include[HTML_REMOVED]

using namespace std;
int main(){
char a[100000];int b[200]={0};
int i,n,l;
cin>>a;
l=strlen(a);
for(i=0;i<l;i)
b[a[i]];

 for(i=0;i<l;i++){
if(b[a[i]]==1){cout<<a[i];return 0;}}//遇return 0;该函数终止;
cout<<"no";

return 0;

}