#include <bits/stdc++.h>
#define FI first
#define SE second
#define PB push_back
#define ll long long
#define FOR(i,a,b) for(int i=a;i<b;i++)
#define ROF(i,a,b) for(int i=b-1;i>=a;i--)
#define YES(i) cout<<(i?"YES":"NO")<<endl
#define Yes(i) cout<<(i?"Yes":"No")<<endl
#define co(i) cout<<(i)<<endl
#define fcout cout<<fixed<<setprecision(10)
#define uni(i) i.erase(unique(i.begin(), i.end()), i.end());
#define all(i) i.begin(),i.end()
using namespace std;

const int INF=1e9+7;
const int MOD=1e9+7;

int main(){
    string s; cin>>s;
    int a[28]={};
    FOR(i,0,s.size()){
        a[s[i]-'A']++;
    }
    bool flag=true;
    FOR(i,0,28){
        if(a[i]>1) flag=false;
    }
    YES(flag);
}