#include <bits/stdc++.h>
using namespace std;
int main() {
int n,cnt=0;
cin>>n;
string s; cin>>s;
for(int i=0 ; i<s.length() ; ++i){
if(s[i]>='A' && s[i]<='Z')s[i]+=32;
}
sort(s.begin() , s.end());
char c='a';
for(int i=0 ; i<s.length() ; ++i){
if(s[i]==c){
c=c+1;
cnt++;
}
}
if(cnt==26)cout<<"YES";
else
cout<<"NO";
return 0;
}
I2luY2x1ZGUgPGJpdHMvc3RkYysrLmg+CnVzaW5nIG5hbWVzcGFjZSBzdGQ7CgppbnQgbWFpbigpIHsKCWludCBuLGNudD0wOwoJY2luPj5uOwoJc3RyaW5nIHM7IGNpbj4+czsKCWZvcihpbnQgaT0wIDsgaTxzLmxlbmd0aCgpIDsgKytpKXsKCQlpZihzW2ldPj0nQScgJiYgc1tpXTw9J1onKXNbaV0rPTMyOwoJfQoJc29ydChzLmJlZ2luKCkgLCBzLmVuZCgpKTsKCWNoYXIgYz0nYSc7Cglmb3IoaW50IGk9MCA7IGk8cy5sZW5ndGgoKSA7ICsraSl7CgkJaWYoc1tpXT09Yyl7CgkJCWM9YysxOwoJCQljbnQrKzsKCQl9Cgl9CglpZihjbnQ9PTI2KWNvdXQ8PCJZRVMiOwoJZWxzZQoJY291dDw8Ik5PIjsKCXJldHVybiAwOwp9