function pangrams(s: string): string {
    const ALPHABET_LENGTH = 26;
    const IS_PANGRAM = 'pangram';
    const IS_NOT_PANGRAM = 'not pangram'
    
    const isValidChar = (char: string): boolean => char !== ' ';
    
    return new Set(s
        .split('')
        .reduce((acc, char) => {
        return isValidChar(char) ? [...acc, char.toLowerCase()] : acc;
    }, [])).size === ALPHABET_LENGTH ? IS_PANGRAM : IS_NOT_PANGRAM;  
}