#include <stdio.h>
#include <math.h>
/*1-d closest pairs*/
/*Based on Shamos & Preparata, p. 190*/

#define MAXPOINTS 2001
#define distance(x1,x2) fabs(x1-x2)

void quickSelection(Xx,numPoints,middle)
float *Xx;
int numPoints,middle;
/*Does quicksort partitioning until element with indicated
  final position in sorted array is positioned*/
/*Also repositions Xx with left elements <= median
  & right elements >= median*/
/*See CLR, p. 154*/
{
int p,r,i,j;
float x,temp;

p=0;
r=numPoints-1;
for (;p<r;)
{
  x=Xx[p];
  i=p-1;
  j=r+1;
  for (;;)
  {
    for (j--;Xx[j]>x;j--);
    for (i++;Xx[i]<x;i++);
    if (i<j)
    {
      temp=Xx[i];
      Xx[i]=Xx[j];
      Xx[j]=temp;
    }
    else
      break;
  }
  if (j>=middle)
    r=j;
  else
    p=j+1;
}
}

void closestPair(Xx,numPoints,closestX1,closestX2,closestDist)
float *Xx;
int numPoints;
float *closestX1,*closestX2,*closestDist;
{
int i,j,k;
float dist;

/*When dividing input,the X arrays are simply handled with pointers
  to the input array*/
float *Xlx,*Xrx;
int numPointsL,numPointsR;  /*Sizes for the divided input*/
/*The next two declarations are for the results of the
  recursive calls*/
float closestLx1,closestLx2,Ldistance;
float closestRx1,closestRx2,Rdistance;
float temp;

if (numPoints<=1)
{
  *closestDist=999999999;
  return;
}

/*divide*/
numPointsL=(numPoints+1)/2;
numPointsR=numPoints/2;
/*Compute beginnings of "new" arrays*/
Xlx=Xx;
/*Skip over left side elements (ptr arithmetic)*/
Xrx=Xx+numPointsL;
/*Reposition elements WRT median*/
quickSelection(Xx,numPoints,numPointsL-1);

/*conquer*/
closestPair(Xlx,numPointsL,&closestLx1,&closestLx2,&Ldistance);
closestPair(Xrx,numPointsR,&closestRx1,&closestRx2,&Rdistance);
/*Use the closer pair*/
if (Ldistance<Rdistance)
{
  *closestDist=Ldistance;
  *closestX1=closestLx1;
  *closestX2=closestLx2;
}
else
{
  *closestDist=Rdistance;
  *closestX1=closestRx1;
  *closestX2=closestRx2;
}

/*combine*/
dist=distance(Xlx[numPointsL-1],Xrx[0]);
if (dist< *closestDist)
{
  *closestDist=dist;
  *closestX1=Xlx[numPointsL-1];
  *closestX2=Xrx[0];
}
}

void main()
{
int numPoints,i;
float points[MAXPOINTS],closest1,closest2,dist;

scanf("%d",&numPoints);
for (i=0;i<numPoints;i++)
  scanf("%f",&points[i]);

closestPair(points,numPoints,&closest1,&closest2,&dist);
printf("The closest points are %f & %f\nat distance %f\n",
  closest1,closest2,dist);
}