Is there a simpler way to write this script? (C programming)

I'm pretty new with C, so I wanted some advice.

This code is looking if the words are anagrams or no. The code threats upper-case input the same as lower-case and it ignores if the input character is not a letter. At the end it should and it does show are the words anagrams or no.

I was wondering is there an easier way to write this code or is this pretty much it?

int alphabet[26] = {0}, sum = 0;
char first[20], second[20];
int i = 0;

printf("Enter the first word: ");
do
{
    first[i] = getchar();
    if(isalpha(first[i]))
    alphabet[toupper(first[i]) - 'A'] += 1 ;
    i++;

}while(first[i - 1] != '\n');

printf("Enter the second word: ");
i = 0;
do
{
    second[i] = getchar();

    if(isalpha(second[i]) && alphabet[toupper(second[i]) - 'A'] > 0)
    {
        alphabet[toupper(second[i]) - 'A'] -= 1;
    }
    i++;

}while(second[i - 1] != '\n');

for(i = 0; i <= 26 - 1; i++)
{
    sum += alphabet[i];
}
if (sum == 0)
    printf("Anagrams\n");
if (sum != 0)
    printf("Not anagrams\n");