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 *= i
    res %= 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 {
  var i = 1
  var res = 1
  while i <= v {
    res *= a
    i += 1
  }
  return res
}
for i in 0...K {
  sum += powd(25, i) * choose(i + S - 1, S - 1) * powd(26, K - i) % 1000000007
}
print(sum)