#include <stdio.h>
int main(void){
    char s[1000];
    int count;
    int flag=0;
    scanf("%s",s);
    for(count=0;s[count]!='\0';count++){
    if(count%2==0&&s[count]==' '){}
    else if(count%2==1&&'a'<=s[count]&&s[count]<='z'){}
    else{flag=1;break;}
    }
    if(flag==0){printf("Yes\n");}
    else{printf("No\n");}
    return 0;
}