C :

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define maxn 210

typedef struct bign{
int a[maxn];
int len;
}bign;

bign getbign(char temp[]){
bign A;
A.len = 0;
memset(A.a,0,sizeof(A.a));
for(int i = strlen(temp)-1;i >= 0; i--) {
    A.a[A.len++] = temp[i]-48;
}
return A;
}

bign add_bign(bign A, bign B) {
int carry = 0;
bign C;
C.len=0;
memset(C.a,0,sizeof(C.a));
for(int i = 0;i < A.len || i < B.len; i++) {
    int temp = A.a[i] + B.a[i] + carry;
    C.a[C.len++] = temp % 10;
    carry = temp / 10;
}
if(carry != 0){
    C.a[C.len++] = carry;
}
return C;
}

bign multi_bign(bign A, int B){
bign C;
C.len = 0;
memset(C.a,0,sizeof(C.a));
int carry = 0;
for(int i = 0;i < A.len; i++) {
    int temp = A.a[i] * B + carry;
    C.a[C.len++] = temp % 10;
    carry = temp / 10;
}
while(carry != 0) {
    C.a[C.len++] = carry % 10;
    carry /= 10;
}
return C;
}

bign div_bign(bign A, int B) {
bign C;
C.len = A.len;
memset(C.a,0,sizeof(C.a));
int r = 0;
for(int i = A.len - 1;i >= 0; i--) {
    r = r*10 + A.a[i];
    if(r < B)C.a[i] = 0;
    else {
        C.a[i] = r / B;
        r = r % B;
    }
}
while(C.len - 1 >= 1 && C.a[C.len - 1] == 0) {
    C.len--;
}
return C;
}

bign multi(bign A, bign B) {
bign C;
C.len = 0;
memset(C.a,0,sizeof(C.a));
bign carry;
carry.len = 0;
memset(carry.a,0,sizeof(carry.a));
for(int i = 0;i < A.len; i++) {
    bign temp = add_bign(multi_bign(B,A.a[i]),carry);
    C.a[C.len++] = temp.a[0];
    carry = div_bign(temp,10);
}
while(carry.len>1 || (carry.len==1 && carry.a[0]!=0)) {
    C.a[C.len++] = carry.a[0];
    carry = div_bign(carry,10);
}
while(C.a[C.len-1]==0 && C.len>1)C.len--;
return C;
}

void print(bign A) {
for(int i = A.len-1;i >= 0; i--){
    printf("%d",A.a[i]);
}
printf("\n");
}

int main()
{
    char temp[maxn];
    while(scanf("%s",temp) != EOF) {
        bign A = getbign(temp);
        scanf("%s",temp);
        bign B = getbign(temp);
        print(multi(A,B));
    }
    return 0;
}

C++ :

#include<iostream>
using namespace std;
string x1,x2;
long j[201],x[101],y[101];
int a,b,c,d,pd;
void djcheng(int b,int z)
{
     int e;
     for (e=z;e<=a+z;e++)
    {
        j[e]+=x[e-z]*b;
        j[e+1]+=(j[e]/10);
        j[e]=j[e]%10;
    }
}
int main()
{
    cin>>x1>>x2;
    a=x1.length()-1;
    b=x2.length()-1;
    for (c=0;c<=a;c++) x[a-c]=x1[c]-'0';
    for (c=0;c<=b;c++) y[b-c]=x2[c]-'0';
    for (c=0;c<=b;c++)
    {
        djcheng(y[c],c);
    }
    pd=a+b+1;
    if (j[pd]==0) pd--;
    if ((x1[0]=='0') || (x2[0]=='0')) cout<<"0";
    else for (c=pd;c>=0;c--) cout<<j[c];
    //system("pause");
    return 0;
}

Pascal :

var a,b,c:array[1..2000] of longint;
    s1,s2,s3:string;
    la,lb,lc,i,j,t:longint;
begin
  readln(s1);
  readln(s2);
  la:=length(s1); lb:=length(s2);
  if (la<lb) or (la=lb) and (s1<s2) then
  begin
    s3:=s1; s1:=s2; s2:=s3;
    la:=length(s1); lb:=length(s2);
  end;
  for i:=1 to la do
    a[la+1-i]:=ord(s1[i])-48;
  for i:=1 to lb do
    b[lb+1-i]:=ord(s2[i])-48;
  for i:=1 to la do
  begin
    t:=0;
    for j:=1 to lb do
    begin
      c[i+j-1]:=c[i+j-1]+a[i]*b[j]+t;
      t:=c[i+j-1] div 10;
      c[i+j-1]:=c[i+j-1] mod 10;
    end;
    c[i+j]:=t;
  end;
  lc:=la+lb;
  while (c[lc]=0) and (lc>1) do dec(lc);
  for i:=lc downto 1 do
    write(c[i]);
  writeln;
end.

Java :

import java.math.BigInteger;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner cin =new Scanner(System.in);
		BigInteger a,b,c;
		a=cin.nextBigInteger();
		b=cin.nextBigInteger();
		c=a.multiply(b);
		System.out.println(c);
	}
}

Python :

# coding=utf-8
s=eval(input())
t=eval(input())
print(s*t)