import java.util.*;
import java.lang.*;
import java.io.*;

public class Main
{
	PrintWriter out = new PrintWriter(System.out);
	BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer tok = new StringTokenizer("");
    String next() throws IOException {
        if (!tok.hasMoreTokens()) { tok = new StringTokenizer(in.readLine()); }
        return tok.nextToken();
    }
    int ni() throws IOException { return Integer.parseInt(next()); }
    long nl() throws IOException { return Long.parseLong(next()); }
    
    void solve() throws IOException {
        for (int tc=1;tc>0;tc--) {
            int n=ni(),x=ni(),t=ni();
            int ans=n/x;
            if (n%x>0) ans++;
            out.println(ans*t);
        }
        out.flush();
    }
    
    public static void main(String[] args) throws IOException {
        new Main().solve();
    }
} import java.util.*; util.* java import java.lang.*; lang.* java import java.io.*; io.* java public class Main
{
	PrintWriter out = new PrintWriter(System.out);
	BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer tok = new StringTokenizer("");
    String next() throws IOException {
        if (!tok.hasMoreTokens()) { tok = new StringTokenizer(in.readLine()); }
        return tok.nextToken();
    }
    int ni() throws IOException { return Integer.parseInt(next()); }
    long nl() throws IOException { return Long.parseLong(next()); }
    
    void solve() throws IOException {
        for (int tc=1;tc>0;tc--) {
            int n=ni(),x=ni(),t=ni();
            int ans=n/x;
            if (n%x>0) ans++;
            out.println(ans*t);
        }
        out.flush();
    }
    
    public static void main(String[] args) throws IOException {
        new Main().solve();
    }
} Main PrintWriter out = new PrintWriter(System.out); out new PrintWriter(System.out) BufferedReader in = new BufferedReader(new InputStreamReader(System.in)); in new BufferedReader(new InputStreamReader(System.in)) StringTokenizer tok = new StringTokenizer(""); tok new StringTokenizer("") String next() throws IOException {
        if (!tok.hasMoreTokens()) { tok = new StringTokenizer(in.readLine()); }
        return tok.nextToken();
    } next {
        if (!tok.hasMoreTokens()) { tok = new StringTokenizer(in.readLine()); }
        return tok.nextToken();
    } if (!tok.hasMoreTokens()) { tok = new StringTokenizer(in.readLine()); } !tok.hasMoreTokens() tok.hasMoreTokens() tok.hasMoreTokens tok { tok = new StringTokenizer(in.readLine()); } tok = new StringTokenizer(in.readLine()) tok new StringTokenizer(in.readLine()) return tok.nextToken(); tok.nextToken() tok.nextToken tok int ni() throws IOException { return Integer.parseInt(next()); } ni { return Integer.parseInt(next()); } return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next long nl() throws IOException { return Long.parseLong(next()); } nl { return Long.parseLong(next()); } return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next void solve() throws IOException {
        for (int tc=1;tc>0;tc--) {
            int n=ni(),x=ni(),t=ni();
            int ans=n/x;
            if (n%x>0) ans++;
            out.println(ans*t);
        }
        out.flush();
    } solve {
        for (int tc=1;tc>0;tc--) {
            int n=ni(),x=ni(),t=ni();
            int ans=n/x;
            if (n%x>0) ans++;
            out.println(ans*t);
        }
        out.flush();
    } for (int tc=1;tc>0;tc--) {
            int n=ni(),x=ni(),t=ni();
            int ans=n/x;
            if (n%x>0) ans++;
            out.println(ans*t);
        } int tc=1; int tc=1; tc 1 tc>0 tc 0 tc-- tc-- tc {
            int n=ni(),x=ni(),t=ni();
            int ans=n/x;
            if (n%x>0) ans++;
            out.println(ans*t);
        } {
            int n=ni(),x=ni(),t=ni();
            int ans=n/x;
            if (n%x>0) ans++;
            out.println(ans*t);
        } int n=ni() n ni() ni x=ni() x ni() ni t=ni(); t ni() ni int ans=n/x; ans n/x n x if (n%x>0) ans++; n%x>0 n%x n x 0 ans++ ans out.println(ans*t) out.println out ans*t ans t out.flush() out.flush out public static void main(String[] args) throws IOException {
        new Main().solve();
    } main {
        new Main().solve();
    } new Main().solve() new Main().solve new Main() String[] args args public class Main
{
	PrintWriter out = new PrintWriter(System.out);
	BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer tok = new StringTokenizer("");
    String next() throws IOException {
        if (!tok.hasMoreTokens()) { tok = new StringTokenizer(in.readLine()); }
        return tok.nextToken();
    }
    int ni() throws IOException { return Integer.parseInt(next()); }
    long nl() throws IOException { return Long.parseLong(next()); }
    
    void solve() throws IOException {
        for (int tc=1;tc>0;tc--) {
            int n=ni(),x=ni(),t=ni();
            int ans=n/x;
            if (n%x>0) ans++;
            out.println(ans*t);
        }
        out.flush();
    }
    
    public static void main(String[] args) throws IOException {
        new Main().solve();
    }
} public class Main
{
	PrintWriter out = new PrintWriter(System.out);
	BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer tok = new StringTokenizer("");
    String next() throws IOException {
        if (!tok.hasMoreTokens()) { tok = new StringTokenizer(in.readLine()); }
        return tok.nextToken();
    }
    int ni() throws IOException { return Integer.parseInt(next()); }
    long nl() throws IOException { return Long.parseLong(next()); }
    
    void solve() throws IOException {
        for (int tc=1;tc>0;tc--) {
            int n=ni(),x=ni(),t=ni();
            int ans=n/x;
            if (n%x>0) ans++;
            out.println(ans*t);
        }
        out.flush();
    }
    
    public static void main(String[] args) throws IOException {
        new Main().solve();
    }
} Main
import java.util.*;
import java.lang.*;
import java.io.*;

public class Main
{
	PrintWriter out = new PrintWriter(System.out);
	BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer tok = new StringTokenizer("");
    String next() throws IOException {
        if (!tok.hasMoreTokens()) { tok = new StringTokenizer(in.readLine()); }
        return tok.nextToken();
    }
    int ni() throws IOException { return Integer.parseInt(next()); }
    long nl() throws IOException { return Long.parseLong(next()); }
    
    void solve() throws IOException {
        for (int tc=1;tc>0;tc--) {
            int n=ni(),x=ni(),t=ni();
            int ans=n/x;
            if (n%x>0) ans++;
            out.println(ans*t);
        }
        out.flush();
    }
    
    public static void main(String[] args) throws IOException {
        new Main().solve();
    }
}