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

int main(){
    string s;
    getline(cin, s);
    bool f = true;
    for(int i = 0; i < s.size(); i++){
        if(i % 2){
            if(s[i] != ' ') f = false;
        }else{
            if(!('a' <= s[i] && s[i] <= 'z')) f = false;
        }
    }
    cout << (f ? "Yes" : "No") << endl;
}