function Main(input) {
	let[N,X,T] = input.split(" ");
  	N = Number(N)
 	X = Number(X)
  	T = Number(T)
  	
  	const reminder = N%X
    const quotient = Math.floor(N/X)
    
    if(reminder==0){
    	console.log(quotient*T)
    }else{
      	console.log((quotient+1)*T)
    }
	
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));