#include <stdio.h>

#include <ctype.h>

int main(void) {

    char s[512], t[512];

    int c, i=0, j=0;

    printf("Enter a string: ");

    while((c=getchar())!='\n' && c!=EOF) { if(i<511) s[i++]=(char)c; }

    s[i]='\0';

    for (i=0; s[i]; ++i) {

        if (isalnum((unsigned char)s[i])) t[j++] = tolower((unsigned char)s[i]);

    }

    t[j]='\0';

    int l=0, r=j-1, ok=1;

    while(l<r){ if(t[l]!=t[r]){ok=0;break;} ++l; --r; }

    printf("%s\n", ok ? "Palindrome" : "Not a palindrome");

    return 0;

}