function triplets(a, b, c) {
  let cleanA = [...new Set(a)].sort((a, b) => a - b)
  let cleanB = [...new Set(b)].sort((a, b) => a - b)
  let cleanC = [...new Set(c)].sort((a, b) => a - b)

  let count = 0
  for (let i = 0; i < cleanB.length; i++) {
    let howManyA = cleanA.findIndex(v => v > cleanB[i])
    let howManyC = cleanC.findIndex(v => v > cleanB[i])
    if (howManyA == -1) howManyA = cleanA.length
    if (howManyC == -1) howManyC = cleanC.length
    
    count += howManyA * howManyC
  }
  return count
}