const getGets = arr => {
  let index = 0

  return () => {
    const toReturn = arr[index]
    index += 1
    return toReturn
  }
}
// this is the test
const test = ['18446744073709551615']

const gets = this.gets || getGets(test)
const print = this.print || console.log

let digits = []

for (let i = 65; i <= 90; i++) {
  digits.push(String.fromCharCode(i))
}

for (let i = 97; i <= 122; i++) {
  for (let j = 65; j <= 90; j++) {
    digits.push(String.fromCharCode(i) + String.fromCharCode(j))
  }
}

let n = BigInt(gets())
let divider = BigInt(256)
let result = []

do {
  result.unshift(digits[n % divider])
  n = ~~(n / divider)
} while (n > 0)

print(result.join(''))