function Main(input){
  input=input.trim();
  const n = input.split(" ");
  if(n<1000){
    console.log("ABC");
  }else{
    console.log("ABD");       
  }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));





function main(input) {
  const tmp = input.trim().split(' ')
  const a = parseInt(tmp[0], 10)
  const b = parseInt(tmp[1], 10)
 
  let answer = Math.max(a + b, a - b, a * b)
  if (answer == 0) {
    console.log(0)
  } else {
    console.log(answer)
  }
}
 
main(require('fs').readFileSync('/dev/stdin', 'utf8'))


function Main(input){
  const a = input.trim().split(" ");
  const n = parseInt(a[0], 10),
        m = parseInt(a[1], 10);
  let ans = Math.max(n+m, n-m, n*m);
  if(ans==0){
  		console.log(0);
  }else{
    console.log(ans);
  }
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));