#include<iostream> #include<vector> #include<algorithm> #include<functional> #include<queue> #include<stack> #include<set> #include<climits> #include<cstdlib> #include<cmath> #include<string> using namespace std; #define INF 1 << 29 #define LL long long int LL const MOD = 1000000007; int main(){ cin.tie(0); ios::sync_with_stdio(false); string str; cin >> str; vector<LL> c(30,0); for(int i = 0; i < str.size(); i++){ c[str[i] - 'A']++; if(c[str[i] - 'A'] > 1){ cout << "NO" << endl; return 0; } } cout << "YES" << endl; return 0; }