#include <bits/stdc++.h>
using namespace std;
template<typename T> inline bool chmax(T& a,T b) { if (a < b) { a = b; return true; } return false; }
template<typename T> inline bool chmin(T& a,T b) { if (a > b) { a = b; return true; } return false; }
const int INF = 1e9;

int main() {
    string S;
    bool judge = true;
    int cnt = 0;
    while (true) {
        cin >> S;
        judge = (S.length()==1);
        cnt++;
        if (55 < cnt) break;
    }
    cout << ((judge) ? "Yes" : "No") << endl;
    return 0;
}