
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.PriorityQueue;
import java.util.StringTokenizer;



public class Main{
	




	public static void main(String[] args) throws IOException {
		
		
		FastScanner sc=new FastScanner();
		
		int n = sc.nextInt();
		int x = sc.nextInt(),t = sc.nextInt();
		int val = n/x * t;
		if(n%x != 0)
			val+=t;
		System.out.println(val);
		
		
	}
	
	
	
	
 
	static void sort(int[] a) {
		ArrayList<Integer> l=new ArrayList<>();
		for (int i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	}
	
	static class FastScanner {
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st=new StringTokenizer("");
		String next() {
			while (!st.hasMoreTokens())
				try {
					st=new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			return st.nextToken();
		}
		
		int nextInt() {
			return Integer.parseInt(next());
		}
		int[] readArray(int n) {
			int[] a=new int[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
		}
		long[] readArrayLong(int n) {
        	long[] a=new long[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
        }
		long nextLong() {
			return Long.parseLong(next());
		}
		String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io import java.util.ArrayList; ArrayList java.util import java.util.Arrays; Arrays java.util import java.util.Collections; Collections java.util import java.util.HashMap; HashMap java.util import java.util.HashSet; HashSet java.util import java.util.List; List java.util import java.util.PriorityQueue; PriorityQueue java.util import java.util.StringTokenizer; StringTokenizer java.util public class Main{
	




	public static void main(String[] args) throws IOException {
		
		
		FastScanner sc=new FastScanner();
		
		int n = sc.nextInt();
		int x = sc.nextInt(),t = sc.nextInt();
		int val = n/x * t;
		if(n%x != 0)
			val+=t;
		System.out.println(val);
		
		
	}
	
	
	
	
 
	static void sort(int[] a) {
		ArrayList<Integer> l=new ArrayList<>();
		for (int i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	}
	
	static class FastScanner {
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st=new StringTokenizer("");
		String next() {
			while (!st.hasMoreTokens())
				try {
					st=new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			return st.nextToken();
		}
		
		int nextInt() {
			return Integer.parseInt(next());
		}
		int[] readArray(int n) {
			int[] a=new int[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
		}
		long[] readArrayLong(int n) {
        	long[] a=new long[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
        }
		long nextLong() {
			return Long.parseLong(next());
		}
		String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
	}
} Main public static void main(String[] args) throws IOException {
		
		
		FastScanner sc=new FastScanner();
		
		int n = sc.nextInt();
		int x = sc.nextInt(),t = sc.nextInt();
		int val = n/x * t;
		if(n%x != 0)
			val+=t;
		System.out.println(val);
		
		
	} main {
		
		
		FastScanner sc=new FastScanner();
		
		int n = sc.nextInt();
		int x = sc.nextInt(),t = sc.nextInt();
		int val = n/x * t;
		if(n%x != 0)
			val+=t;
		System.out.println(val);
		
		
	} FastScanner sc=new FastScanner(); sc new FastScanner() int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int x = sc.nextInt() x sc.nextInt() sc.nextInt sc t = sc.nextInt(); t sc.nextInt() sc.nextInt sc int val = n/x * t; val n/x * t n/x n x t if(n%x != 0)
			val+=t; n%x != 0 n%x n x 0 val+=t val t System.out.println(val) System.out.println System.out System System.out val String[] args args static void sort(int[] a) {
		ArrayList<Integer> l=new ArrayList<>();
		for (int i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	} sort {
		ArrayList<Integer> l=new ArrayList<>();
		for (int i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	} ArrayList<Integer> l=new ArrayList<>(); l new ArrayList<>() for (int i:a) l.add(i); int i a l.add(i); l.add(i) l.add l i Collections.sort(l) Collections.sort Collections l for (int i=0; i<a.length; i++) a[i]=l.get(i); int i=0; int i=0; i 0 i<a.length i a.length a a.length i++ i++ i a[i]=l.get(i); a[i]=l.get(i) a[i] a i l.get(i) l.get l i int[] a a static class FastScanner {
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st=new StringTokenizer("");
		String next() {
			while (!st.hasMoreTokens())
				try {
					st=new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			return st.nextToken();
		}
		
		int nextInt() {
			return Integer.parseInt(next());
		}
		int[] readArray(int n) {
			int[] a=new int[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
		}
		long[] readArrayLong(int n) {
        	long[] a=new long[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
        }
		long nextLong() {
			return Long.parseLong(next());
		}
		String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
	} FastScanner BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) StringTokenizer st=new StringTokenizer(""); st new StringTokenizer("") String next() {
			while (!st.hasMoreTokens())
				try {
					st=new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			return st.nextToken();
		} next {
			while (!st.hasMoreTokens())
				try {
					st=new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			return st.nextToken();
		} while (!st.hasMoreTokens())
				try {
					st=new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				} !st.hasMoreTokens() st.hasMoreTokens() st.hasMoreTokens st try {
					st=new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				} catch (IOException e) {
					e.printStackTrace();
				} IOException e {
					e.printStackTrace();
				} e.printStackTrace() e.printStackTrace e {
					st=new StringTokenizer(br.readLine());
				} st=new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st int nextInt() {
			return Integer.parseInt(next());
		} nextInt {
			return Integer.parseInt(next());
		} return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next int[] readArray(int n) {
			int[] a=new int[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
		} readArray {
			int[] a=new int[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
		} int[] a=new int[n]; a new int[n] n for (int i=0; i<n; i++) a[i]=nextInt(); int i=0; int i=0; i 0 i<n i n i++ i++ i a[i]=nextInt(); a[i]=nextInt() a[i] a i nextInt() nextInt return a; a int n n long[] readArrayLong(int n) {
        	long[] a=new long[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
        } readArrayLong {
        	long[] a=new long[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
        } long[] a=new long[n]; a new long[n] n for (int i=0; i<n; i++) a[i]=nextInt(); int i=0; int i=0; i 0 i<n i n i++ i++ i a[i]=nextInt(); a[i]=nextInt() a[i] a i nextInt() nextInt return a; a int n n long nextLong() {
			return Long.parseLong(next());
		} nextLong {
			return Long.parseLong(next());
		} return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        } nextLine {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        } String str = ""; str "" try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } IOException e {
                e.printStackTrace();
            } e.printStackTrace() e.printStackTrace e {
                str = br.readLine();
            } str = br.readLine() str br.readLine() br.readLine br return str; str public class Main{
	




	public static void main(String[] args) throws IOException {
		
		
		FastScanner sc=new FastScanner();
		
		int n = sc.nextInt();
		int x = sc.nextInt(),t = sc.nextInt();
		int val = n/x * t;
		if(n%x != 0)
			val+=t;
		System.out.println(val);
		
		
	}
	
	
	
	
 
	static void sort(int[] a) {
		ArrayList<Integer> l=new ArrayList<>();
		for (int i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	}
	
	static class FastScanner {
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st=new StringTokenizer("");
		String next() {
			while (!st.hasMoreTokens())
				try {
					st=new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			return st.nextToken();
		}
		
		int nextInt() {
			return Integer.parseInt(next());
		}
		int[] readArray(int n) {
			int[] a=new int[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
		}
		long[] readArrayLong(int n) {
        	long[] a=new long[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
        }
		long nextLong() {
			return Long.parseLong(next());
		}
		String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
	}
} public class Main{
	




	public static void main(String[] args) throws IOException {
		
		
		FastScanner sc=new FastScanner();
		
		int n = sc.nextInt();
		int x = sc.nextInt(),t = sc.nextInt();
		int val = n/x * t;
		if(n%x != 0)
			val+=t;
		System.out.println(val);
		
		
	}
	
	
	
	
 
	static void sort(int[] a) {
		ArrayList<Integer> l=new ArrayList<>();
		for (int i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	}
	
	static class FastScanner {
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st=new StringTokenizer("");
		String next() {
			while (!st.hasMoreTokens())
				try {
					st=new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			return st.nextToken();
		}
		
		int nextInt() {
			return Integer.parseInt(next());
		}
		int[] readArray(int n) {
			int[] a=new int[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
		}
		long[] readArrayLong(int n) {
        	long[] a=new long[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
        }
		long nextLong() {
			return Long.parseLong(next());
		}
		String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
	}
} Main

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.PriorityQueue;
import java.util.StringTokenizer;



public class Main{
	




	public static void main(String[] args) throws IOException {
		
		
		FastScanner sc=new FastScanner();
		
		int n = sc.nextInt();
		int x = sc.nextInt(),t = sc.nextInt();
		int val = n/x * t;
		if(n%x != 0)
			val+=t;
		System.out.println(val);
		
		
	}
	
	
	
	
 
	static void sort(int[] a) {
		ArrayList<Integer> l=new ArrayList<>();
		for (int i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	}
	
	static class FastScanner {
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st=new StringTokenizer("");
		String next() {
			while (!st.hasMoreTokens())
				try {
					st=new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			return st.nextToken();
		}
		
		int nextInt() {
			return Integer.parseInt(next());
		}
		int[] readArray(int n) {
			int[] a=new int[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
		}
		long[] readArrayLong(int n) {
        	long[] a=new long[n];
			for (int i=0; i<n; i++) a[i]=nextInt();
			return a;
        }
		long nextLong() {
			return Long.parseLong(next());
		}
		String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
	}
}
