A

#include <bits/stdc++.h>

using namespace std;

int main()
{
    string s;
    cin>>s;

    int f = 1;

    for(int i=1; i<s.size(); i++)
        f &= (s[i] < s[i-1]);

    if(f)       cout<<"Yes\n";
    else        cout<<"No\n";
}