Problem:
Score : 200 points

Problem Statement

Given N integers A_1, ..., A_N, compute A_1 \times ... \times A_N.

However, if the result exceeds 10^{18}, print -1 instead.

Constraints

2 \leq N \leq 10^5

0 \leq A_i \leq 10^{18}

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
A_1 ... A_N

Output

Print the value A_1 \times ... \times A_N as an integer, or -1 if the value exceeds 10^{18}.

Sample Input 1

2
1000000000 1000000000

Sample Output 1

1000000000000000000

We have 1000000000 \times 1000000000 = 1000000000000000000.

Sample Input 2

3
101 9901 999999000001

Sample Output 2

-1

We have 101 \times 9901 \times 999999000001 = 1000000000000000001, which exceeds 10^{18}, so we should print -1 instead.

Sample Input 3

31
4 1 5 9 2 6 5 3 5 8 9 7 9 3 2 3 8 4 6 2 6 4 3 3 8 3 2 7 9 5 0

Sample Output 3

0

Solution in Go (1.14.1) (judge verdict: Wrong Answer)

package main

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

func main() {
	sc := NewBufScanner(os.Stdin)
	n := int(sc.Int())

	var a int64
	sum := big.NewInt(1)

	upper := big.NewInt(1e18)
	as := make([]int64, n)
	for i := 0; i < n; i++ {
		as[i] = sc.Int()
		if a == 0 {
			fmt.Println(0)
			return
		}
	}
	for i, v := range  as {
		if i == 0 {
			sum = big.NewInt(v)
			continue
		}
		sum.Mul(sum, big.NewInt(v))
		if sum.Cmp(upper) >0 {
			fmt.Println("-1")
			return
		}
	}
	fmt.Println(sum.Int64())
}

type BufScanner struct {
	*bufio.Scanner
}

func NewBufScanner(r io.Reader) *BufScanner {
	s := bufio.NewScanner(r)
	s.Split(bufio.ScanWords)
	// s.Split(scanWords)
	return &BufScanner{s}
}

func scanWords(data []byte, atEOF bool) (advance int, token []byte, err error) {
	start := 0
	for isSpace(data[start]) {
		start++
	}
	for i := start; i < len(data); i++ {
		if isSpace(data[i]) {
			return i+1, data[start:i], nil
		}
	}
	if atEOF && len(data) > start {
		return len(data), data[start:], nil
	}
	return start, nil, nil
}
func isSpace(b byte) bool {
	return b == ' ' || b == '\n' || b == '\r' || b == '\t'
}

func (s *BufScanner) String() string {
	s.Scan()
	return s.Text()
}

func (s *BufScanner) Int() int64 {
	return int64(s.UInt())
}


func (s *BufScanner) UInt() uint64 {
	s.Scan()
	i, e := strconv.ParseUint(s.Text(), 10, 64)
	if e != nil {
		panic(e)
	}
	return i
}