C :

#include<stdio.h>
#include<string.h>
int change(char*c)
{
	if(strlen(c)==0)
	return 1;	
	int i,s=0;
	for(i=0;i<strlen(c);i++)
	{
		s=s*10+c[i]-'0';
	}
	return s;
}
main()
{
	char a[100];
	char b[100];
	gets(a);
	int i,k=0,j;
	for(i=0;i<strlen(a);i++)
	{
		if(a[i]>='0'&&a[i]<='9')
		{
			b[k]=a[i];
			k++;
		}
		else
		{
			b[k]='\0';
			int x=change(b);
			for(j=1;j<=x;j++)
			{
				printf("%c",a[i]);
			}
			k=0;
		}
	}
}

C++ :

#include <iostream>
#include <cstring>
using namespace std;

void scopy(char s[],int m,int n,char r[]){
	int i,k = 0;
	for (i = m;i <= n;i++){
		r[k] = s[i];
		k++;
	}
	r[k] = '\0';
}

int num(char s[]){
	int i,c = 0,t = 1;
	for (i = strlen(s) - 1;i >= 0;i--){
		c = c + (s[i] - 48) * t;
		t = t * 10;
	}
	return c;
}

int main(){
	char a[2000];
	char r[2000];
	gets(a);
	int i,j,k = -1,c;
	for (i = 0;i < strlen(a);i++){
		if (a[i] >= 'a' && a[i] <= 'z'){
			if (i == 0 || a[i - 1] >= 'a' && a[i - 1] <= 'z'){
				//cout<<1<<" "<<a[i]<<endl;
				c = 1;
			}else{
				for (j = i - 1;j >= 0;j--){
					if (a[j] >= 'a' && a[j] <= 'z'){
						k = j;
						break;
					}
				}
				scopy(a,k + 1,i - 1,r);
				//cout<<r<<" "<<a[i]<<endl;
				c = num(r);
			}
			
			for (j = 1;j <= c;j++){
				cout<<a[i];
			}
		}
	}
}

Java :

import java.util.Scanner;

public class Main{

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.nextLine();
		int c = 0;
		int begin = 0;
		for(int i = 0;i < s.length();i++){
			if(s.charAt(i) >= 'a' && s.charAt(i) <= 'z'){
				if(i == 0 || (s.charAt(i - 1) >= 'a' && s.charAt(i) <= 'z')){
					c = 1;
				}else {
					for(int j = i - 1;j >= 0;j--){
						if(s.charAt(j) >= 'a' && s.charAt(j) <= 'z'){
							begin = j + 1;
							break;
						}
					}
					
					String num = s.substring(begin,i);
					c = Integer.parseInt(num);
				}
				
				//System.out.println(s.charAt(i) + " " + c);
				for(int j = 1;j <= c;j++){
					System.out.print(s.charAt(i));
				}
			}
		}
	}
}

Python :

a = input()
s = ''
for i in range(0,len(a)) :
    if a[i].isdigit():
        s = s + a[i]
    else:  
        if s == '':
            print(a[i],end = '')
        else:
            print(a[i]*int(s), end='')
            s = ''