let K = Int(readLine()!)!
let S = readLine()!.count

var sum = 0

func fact(_ a: Int) -> Int {
  if a == 0 {
    return 1
  }
  var res = 1
  for i in 1...a {
    res = res * i % 1000000007
  }
  return res
}

func choose(_ a: Int, _ b: Int) -> Int {
  return fact(a) / (fact(b) * fact(a - b))
}
func powd(_ a: Int, _ v: Int) -> Int {
  if v == 0 {
    return 1
  }
  let half = powd(a, v / 2)
  var res = half * half % 1000000007
  if v & 1 == 1 {
    res = res * a % 1000000007
  }
  return res
}
for i in 0...K {
  sum += (powd(25, i) * choose(i + S - 1, S - 1) * powd(26, K - i)) % 1000000007
}
print(sum)