#include<bits/stdc++.h>
using namespace std;
int main(){
	string s;
	int others=0;
	cin>>s;
	for(int i=0;i<s.length();i++){
			if(s[i]>='0' and s[i]<='9'){
				;
			}else{
				others++;
			}
		}
				if(others==0) cout<<"yes";
				else cout<<"no";
	return 0;
}