function Main(arg) {
  let N = BigInt(arg.trim().split(' ')[0]);
  let X = BigInt(arg.trim().split(' ')[1]);
  let T = BigInt(arg.trim().split(' ')[2]);
  let result = T;
  if(N > X){
    result = N/X*T;
    
    if(N%X != 0){
      result +=T;
    }
  }
  console.log(Number(result));
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));
