#include<stdio.h>
#include<string.h>
#include<ctype.h>
#include<stdlib.h>
int main()
{
    char input[1000];
    fgets(input,sizeof(input),stdin);
    int numbers[100];
    int count = 0;
    char *token = strtok(input,"\n");
    while(token != NULL){
        int i=0;
        if(token [i] == '-')i++;
        for(; token[i] != '\0';i++){
            if(!isdigit(token[i])){
                printf("Invalid input");
                return 0;
            }
        }
        int num=atoi(token);
        if(num == -1)
        break;
        numbers[count++]=num;
        token = strtok(NULL,"\n");
    }
    if(token==null){
        printf("Invalid input \n");
        return 0;
    }
    int ispalindrome=1;
    for(int i=0;i<count/2;i++){
        if(numbers[i] != numbers[count - i -1]){
            ispalindrome = 0;
            break;
        }
    }
    if(ispalindrome)
       printf("yes\n");
       else 
       printf("no\n");
       return 0;
}