#include<iostream>
#include<string>
#include<algorithm>
using namespace std;
typedef unsigned int uint;
// O(N)
bool is_unique3(string line){
uint size = line.size();
if(size>256)return false;
int flag=0;
uint i;
for(i=0;i<size;i++){
int val = line[i]-'a';
if(flag&(1<<val))return false;
flag|=(1<<val);
}
return true;
}
// O(NlogN)
bool is_unique2(string line){
sort(line.begin(),line.end());
uint i;
uint size=line.size();
for(i=1;i<size;i++){
if(line[i-1]==line[i]){
return false;
}
}
return true;
}
// O(N^2)
bool is_unique(string line){
uint size=line.size();
uint i,j;
for(i=0;i<size;i++)
for(j=i+1;j<size;j++)
if(line[i]==line[j])return false;
return true;
}
int main(){
string line;
cin>>line;
if(is_unique3(line))cout<<"unique"<<endl;
else cout<<"not unique"<<endl;
return 0;
}