function calculate(input) {
    var division = input % 26, power = input / 26 | 0,
        out = division ? String.fromCharCode(64 + division) : (--power,'Z');
    return power ? calculate(power) + out : out;
}

console.log(calculate(1)) // A
console.log(calculate(2)) // B

console.log(calculate(702)) // ZZ
console.log(calculate(700)) // ZX

for(i = 1;i < 702;i++) {
  console.log(calculate(i))
}