#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
// Welcome to my source code!

int main() {
    char c[101];
    int i = 0;
    bool flag = true;
    while (cin >> c[i++]) {
        if (i % 2 && c[i] != ' ') flag = false;
    }
    if (flag) cout << "Yes" << endl;
    else cout << "No" << endl;
}