def bigE() {
  BigDecimal e = new BigDecimal(1.0G)
  BigDecimal temp = new BigDecimal(1.0G)
  for (int i in 1..100) {
    temp *= i
    e += new BigDecimal("1")
         .divide(temp, new java.math.MathContext(10000))
  }
  return e.toString()
}
 
def isPrime(long n) {
  if (n < 2) return false
  if (n == 2 || n == 3) return true
  if (n%2 == 0 || n%3 == 0) return false
  long sqrtN = (long)Math.sqrt(n)+1
  for (long i=6L; i < sqrtN; i += 6) {
    if (n%(i-1) == 0 || n%(i+1) == 0) return false
  }
  return true
}
 
def firstPrimeBySize(n) {
  String e = bigE()
  for (int i in 2..e.size()-n) {
    String chunk = e.substring(i,i+n)
    if (isPrime(new BigDecimal(chunk).toLong())) {
      return "$chunk at position $i"
    }
  }
}
 
assert firstPrimeBySize(10) == "7427466391 at position 100"