#include<iostream>
#include<string>
#include<vector>
#include<cctype>
using namespace std;
int main(){
    string s;
    getline(cin,s);
    vector<bool>present(26,false);
    int count =0;
    for(char c:s){
        of(isalpha(c)){
            int index =tolower(c)-'a';
            if(!present [index]){
                present[index]=true;
                cout++;
            }
        }
    }
    if(cout==26){
        cout<<"yes"<<endl;
    }else{
        cout"no"<<endl;
        }
        return 0;
}