export function commonChars(a: string, b: string): number {
  const normalizedA = a.toLowerCase()
  const normalizedB = b.toLowerCase()
  const letters = []
  for (let i =0; i < normalizedA.length;i++){
    if( normalizedB.includes(normalizedA[i]) && !letters.includes(normalizedA[i])) 
      letters.push(normalizedA[i])
  }
  return letters.length;
}