#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* stdio */
int size(char *s){
   int x;
   for(int i = 0;i < 1000000000;i++){
      if(s[i] == NULL){
         x = i;
         break;
      }
   }
   return x;
}

int main(){
   char s[100];
   int flag = 0;
   scanf("%s",&s);
   for(int i = 0;i < size(s);i++){
      if((i%2 == 1)&&(s[i] != " "))flag = 1;
      if((i%2 == 0)&&(!(s[i] >= 97)&& !(s[i] <= 122)))flag = 1;
   }
   if(flag == 1)printf("No\n");
   else printf("Yes\n");
}