#include <bits/stdc++.h>
using namespace std;

int main(){
    bool yes = true;
    string s;
    getline(cin ,s);
    for(int i=0;i<s.size();i++){
        if(i&1) yes &= s[i] == ' ';
        else yes &= s[i] >= 'a' && s[i] <= 'z';
    }
    cout << (yes ? "Yes" : "No") << endl;
    return 0;
}