package main

import (
	"bufio"
	"fmt"
	"math/big"
	"os"
	"strconv"
)

var sc = bufio.NewScanner(os.Stdin)

func main() {
	sc.Split(bufio.ScanWords)
	n := nextInt()
	t := big.NewRat(0, 1)
	for i := 0; i < n; i++ {
		r := new(big.Rat)
		fmt.Sscan(nextLine(), r)
		t.Add(t, r)
	}
	fmt.Println(t.FloatString(10))
}

func nextLine() string {
	sc.Scan()
	return sc.Text()
}

func nextInt() int {
	i, _ := strconv.Atoi(nextLine())
	return i
}