Write a program to display the following pyramid structure

Write a program to display the following pyramid structure using while loop. 
 1
 22
 333
 4444
 55555 

#include <iostream>

using namespace std;

int main(){

       int a = 1;

       while (a<=5)

       {

             

              int b = 1;

              while (b<a){

                    

                     cout << a;

                     b++;

              }

              cout << a << endl;

              a++;

       }

       system("pause");

       return 0;

}