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

public class Main {
    
    public static void main(String[] args) {
        FastScanner sc = new FastScanner();
        int n = sc.nextInt();
        double[][] x = new double[n][2];
        for(int i=0; i<n; i++){
            x[i][0] = sc.nextDouble();
            x[i][1] = sc.nextDouble();
        }

        int num = 1000000;
        double ans = 0.0d;
        for(int i=0; i<num; i++){
            double ang = (double)i / (double)num * 2.0d * Math.PI;
            double mx = Math.cos(ang);
            double my = Math.sin(ang);

            double[] pos = new double[2];
            for(int j=0; j<n; j++){
                if(mx * x[j][0] + my*x[j][1] >= 0){
                    pos[0] += x[j][0];
                    pos[1] += x[j][1];
                }
            }

            double mlen = Math.sqrt(pos[0]*pos[0] + pos[1]*pos[1]);
            ans = Math.max(ans, mlen);
        }

        System.out.println(ans);

    }


    private static class FastScanner {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;

        private boolean hasNextByte() {
            if (ptr < buflen) {
                return true;
            } else {
                ptr = 0;
                try {
                    buflen = in.read(buffer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (buflen <= 0) {
                    return false;
                }
            }
            return true;
        }

        private int readByte() {
            if (hasNextByte())
                return buffer[ptr++];
            else
                return -1;
        }

        private static boolean isPrintableChar(int c) {
            return 33 <= c && c <= 126;
        }

        public boolean hasNext() {
            while (hasNextByte() && !isPrintableChar(buffer[ptr]))
                ptr++;
            return hasNextByte();
        }

        public String next() {
            if (!hasNext())
                throw new NoSuchElementException();
            StringBuilder sb = new StringBuilder();
            int b = readByte();
            while (isPrintableChar(b)) {
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }

        public long nextLong() {
            if (!hasNext())
                throw new NoSuchElementException();
            long n = 0;
            boolean minus = false;
            int b = readByte();
            if (b == '-') {
                minus = true;
                b = readByte();
            }
            if (b < '0' || '9' < b) {
                throw new NumberFormatException();
            }
            while (true) {
                if ('0' <= b && b <= '9') {
                    n *= 10;
                    n += b - '0';
                } else if (b == -1 || !isPrintableChar(b)) {
                    return minus ? -n : n;
                } else {
                    throw new NumberFormatException();
                }
                b = readByte();
            }
        }

        public int nextInt() {
            long nl = nextLong();
            if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
                throw new NumberFormatException();
            return (int) nl;
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }
    }
}


Measured memory_bytes: 43460