Palindrome check

/* C programme to check if a string is palindrome or not */
#include<stdio.h>
#include<string.h>
int main(void)
{
    char a[999];
    gets(a);
    int x=strlen(a);
    int counter=0;
    int i;
    for(i=0;i<=x;i++)
    {
        if(a[i]==a[x-1])
        {
            counter++;
            x--;
        }
    }
    if(i==counter)
    {
        printf("YES\n");
    }
    else
    {
        printf("NO\n");
    }
    return 0;
}
/*
Check if a string is palindrome or not.
Sample input: ulala
Sample output: NO

Sample input: abcba
Sample output: YES
*/