import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.PrintWriter; import java.util.*; public class C { public static void main(String[] args) throws IOException { MyScanner sc = new MyScanner(System.in); String p = sc.next(); int[] ds = new int[20000]; for(int i=0; i=1) { ds[i+1]--; } else { System.out.println("No"); return; } } else { System.out.println("No"); return; } } } static class MyScanner { BufferedReader br; StringTokenizer st; public MyScanner(InputStream s) { br=new BufferedReader(new InputStreamReader(s)); } public String nextLine() throws IOException { return br.readLine(); } public String next() throws IOException { while(st==null || !st.hasMoreTokens()) st=new StringTokenizer(br.readLine()); return st.nextToken(); } public int nextInt() throws IOException { return Integer.parseInt(next()); } public double nextDouble() throws IOException { return Double.parseDouble(next()); } public boolean ready() throws IOException { return br.ready(); } public long nextLong() throws IOException { return Long.parseLong(next()); } } }