import java.util.*;
import java.io.*;
import java.math.*;

class Main{

    static void solve(){

        int n = ni();
        long [] A = new long[n];
        long [] MAX = new long[n];
        for(int i = 0 ; i < n ; i ++ ) {
            A[i] = (long)Math.abs(nl());
        }
        MAX[0] = A[0];
        for(int i = 1 ; i < n ; i++ ) {
            MAX[i] = (long)Math.max(MAX[i-1],A[i]);
        }
        long ans = 0;
        for(int i = 0 ; i < n ; i ++ ) {
            ans += MAX[i];
        }
        output.print(ans);
    }

    // - - - - - - - - - - - - - - - - - - - - - - - - - - - - //

    static int ni(){ return Integer.parseInt(sc.next()); }
    static long nl(){ return Long.parseLong(sc.next()); }
    static double nd(){ return Double.parseDouble(sc.next()); }
    static String ns(){ return sc.next(); }
    static BigInteger bi(){ return sc.nextBigInteger(); }
    static BigDecimal bd(){ return sc.nextBigDecimal(); }

    static PrintWriter output;
    static Scanner sc ;
    public static void main(String[] args){
        output = new PrintWriter(System.out);
        sc = new Scanner(System.in);
        solve();
        output.flush();
    }

}