C :

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>
#include<math.h>
char x[240];
long long y,a[1001];
int main(){
	scanf("%s",&x);
	scanf("%lld",&y);
	int i,k = 0;  
	for(i=strlen(x)-1;i>=0;i--) a[k++] = (x[i]-'0')*y;
	for(i=0;i<k;i++){
		a[i+1] = a[i+1] +  a[i]/10;
		a[i] = a[i]%10;
	} 
	k = 1000;
	for(i=1000;i>=0;i--){
		if(a[i]!=0){
			k = i;
			break;
		}
	}
	if(k==1000) {
		printf("%d",0);
		return 0;
	}
	for(i=k;i>=0;i--){
		printf("%d",a[i]);
	}
	return 0;
}

C++ :

#include <iostream>
#include <cstring>
using namespace std;
 
void diaohuan(char s[],int a[]){
    int i;
    for(i=0;s[i]!='\0';i++){
        a[i]=s[strlen(s)-i-1]-48;
    }
}
 
int main(){
    int i,n;
    char s[260];
    gets(s);
    cin>>n;
    int a[260]={0};
    diaohuan(s,a);
    for(i=0;i<strlen(s);i++){
        a[i]=a[i]*n;
    }
    for(i=0;i<strlen(s)+5;i++){
        if(a[i]>=10){
            a[i+1]=a[i+1]+a[i]/10;
            a[i]=a[i]%10;
        }
    }
    int flag=0;
    for(i=strlen(s)+5;i>=0;i--){
        if(a[i]!=0){
            flag=1;
        } 
        if(flag==1){
            cout<<a[i];
        }
    }
    if(flag==0){
        cout<<0;
    }
}

Java :

import java.util.Scanner;

public class Main {
	static String x;
	static long y;
	static long a[] = new long[1001];
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		x = sc.next();
		y = sc.nextLong();
		int i,k = 0;  
		for(i=x.length()-1;i>=0;i--) a[k++] = (x.charAt(i)-'0')*y;
		for(i=0;i<k;i++){
			a[i+1] = a[i+1] +  a[i]/10;
			a[i] = a[i]%10;
		} 
		k = 1000;
		for(i=1000;i>=0;i--){
			if(a[i]!=0){
				k = i;
				break;
			}
		}
		if(k==1000) {
			System.out.print(0);
			return;
		}
		for(i=k;i>=0;i--){
			System.out.print(a[i]);
		}
		return;	
	}
}

Python :

print(int(input())*int(input()))