function Main(input) {
  input = input.replace(/\n/g, ' ').split(" ");
  var a = Number(input[0]);
  var b = Number(input[1]);
  var c = Number(input[2]);
  var ans =c;
  var mem=b;
  while(true){
    if(mem>=a){
      break;
    }
    ans+=c;
    mem+=b;
  }
  console.log(ans);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));
