// // Created by yamunaku on 2020/04/01. // #include <bits/stdc++.h> using namespace std; #define rep(i, n) for(int i = 0; i < (n); i++) #define repl(i, l, r) for(int i = (l); i < (r); i++) #define per(i, n) for(int i = ((n)-1); i >= 0; i--) #define perl(i, l, r) for(int i = ((r)-1); i >= (l); i--) #define all(x) (x).begin(),(x).end() #define MOD9 998244353 #define MOD1 1000000007 #define IINF 1000000000 #define LINF 1000000000000000000 #define SP <<" "<< #define CYES cout<<"Yes"<<endl #define CNO cout<<"NO"<<endl #define CFS cin.tie(0);ios::sync_with_stdio(false) #define CST(x) cout<<fixed<<setprecision(x) using ll = long long; using ld = long double; using vi = vector<int>; using mti = vector<vector<int>>; using vl = vector<ll>; using mtl = vector<vector<ll>>; using pi = pair<int, int>; using pl = pair<ll, ll>; template<typename T> using heap = priority_queue<T, vector<T>, function<bool(const T, const T)>>; int main(){ //CFS; string s; getline(cin, s); int n = s.size(); if(n == 1){ CNO; return 0; } map<int, int> a, b; int tt = 0; rep(i, n){ if(s[i] != ' ') tt++; if(i & 1){ if(s[i] != ' '){ a[s[i] - 'a'] = true; } }else{ if(s[i] != ' '){ b[s[i] - 'a'] = true; } } } string t = s; int x = tt, y = tt; rep(i, n){ if(a[s[i] - 'a'] && s[i] != ' ') s[i] = ' ', x--; if(b[t[i] - 'a'] && t[i] != ' ') t[i] = ' ', y--; } bool ok1 = true, ok2 = true; if(x == 0) ok1 = false; if(y == 0) ok2 = false; int sta1 = 0, sta2 = 0; rep(i, n){ if(i & 1){ if(t[i] != ' '){ if(sta2 == 2){ ok2 = false; } sta2 = 1; }else{ if(sta2 == 0) sta2 = 2; } }else{ if(s[i] != ' '){ if(sta1 == 2){ ok1 = false; } sta1 = 1; }else{ if(sta1 == 0) sta1 = 2; } } } if(ok1 || ok2) CYES; else CNO; return 0; }