// An isogram is a word, in which no letter of the alphabet 
// occurs more than once. Write a C program that reads in 
// strings until Ctrl+D, and checks whether the string is an isogram. 

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

#define MAX 100

// Sample input/output

// hello
// This is not an isogram
// table
// This is an isogram
// Yay
// This is not an isogram
// CtrlD

int main(void) {
    char line[MAX];

    while (fgets(line, MAX, stdin) != NULL) {
        // count the letters
        int letters[26] = {0};
        int isogram = 1;
        int i = 0;
        while (line[i] != '\0') {
            if (isalpha(line[i])) {
                int index = tolower(line[i]) - 'a';
                letters[index]++;
                if (letters[index] > 1) {
                    isogram = 0;
                }
            }
            i++;
        }

        if (isogram == 0) {
            printf("This is not an isogram.\n");
        } else {
            printf("This is an isogram.\n");
        }
    }
}