Sortare dupa prima cifra

#include <iostream>
#include <fstream>
using namespace std;
///Avem un sir cu n nr naturale. Sortati nr din sir cresc dupa prima cifra:
/*
IN:
6
89 22 91 4005 51 721
OUT:
22 4005 51 721 89 91
  */
int main(){
  ifstream cin("test.in");
  ofstream cout("test.out");
//Andreea -declaratii
  int n,a[501],i,x,y,sumx,sumy,c;
  //Georgiana -citire sir
 cin>>n;
  for (int i=1;i<=n;i++){
    cin >> a[i];
  }
  for(i=1; i<=n; i++){
    for(int j=i+1 ; j<=n ;j++){
      x=a[i];
      y=a[j];
      sumx=0;
      sumy=0;
      ///G
      while(x>=10){
        x=x/10;
        }
      while(y>=10){
        y=y/10;
        }


      if(x>y){
        swap(a[i],a[j]);
      }
    }
  }


//Bianca -afisare sir
  for(i=1; i<=n; i++){
    cout<<a[i] << " ";
  }

}