Problem:
Multiplication of Big Integers II

Given two integers $A$ and $B$, compute the product, $A \times B$.

Input

Two integers $A$ and $B$ separated by a space character are given in a line.

Output

Print the product in a line.

Constraints

$-1 \times 10^{200000} \leq A, B \leq 10^{200000}$

Sample Input 1

5 8

Sample Output 1

40

Sample Input 2

100 25

Sample Output 2

2500

Sample Input 3

-1 0

Sample Output 3

0

Sample Input 4

12 -3

Sample Output 4

-36

Solution in Go (judge verdict: Accepted)

package main

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

func configure(scanner *bufio.Scanner) {
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1000005), 1000005)
}
func getNextString(scanner *bufio.Scanner) string {
	scanned := scanner.Scan()
	if !scanned {
		panic("scan failed")
	}
	return scanner.Text()
}
func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}
func getNextInt64(scanner *bufio.Scanner) int64 {
	i, _ := strconv.ParseInt(getNextString(scanner), 10, 64)
	return i
}
func getNextFloat64(scanner *bufio.Scanner) float64 {
	i, _ := strconv.ParseFloat(getNextString(scanner), 64)
	return i
}
func main() {
	fp := os.Stdin
	wfp := os.Stdout
	extra := 0
	if os.Getenv("I") == "IronMan" {
		fp, _ = os.Open(os.Getenv("END_GAME"))
		extra = 100
	}
	scanner := bufio.NewScanner(fp)
	configure(scanner)
	writer := bufio.NewWriter(wfp)
	defer func() {
		r := recover()
		if r != nil {
			fmt.Fprintln(writer, r)
		}
		writer.Flush()
	}()
	solve(scanner, writer)
	for i := 0; i < extra; i++ {
		fmt.Fprintln(writer, "-----------------------------------")
		solve(scanner, writer)
	}
}
func solve(scanner *bufio.Scanner, writer *bufio.Writer) {
	a := new(big.Int)
	b := new(big.Int)
	fmt.Sscan(getNextString(scanner), a)
	fmt.Sscan(getNextString(scanner), b)
	fmt.Fprintln(writer, a.Mul(a, b))
}