#include <stdio.h>
#define MAX 1000000
typedef struct
{
    int x;
    int y;
} point;
point pt[MAX];
int f[MAX],g[MAX];
int main()
{
    int cases,m,n,i,j,max;
    scanf("%d",&cases);
    for(i=0,max=0; i<cases; i++)
    {
        scanf("%d%d",&pt[i].x,&pt[i].y);
        if(max<pt[i].y)
            max=pt[i].y;
    }
    for(i=0; i<cases; i++)
    {
        m=pt[i].x;
        n=pt[i].y;
        if(m==n)
            g[m]=1;
        else
        {
            for(j=m; j<n; j++)
                f[j]=1;
        }
    }
    for(i=1; i<=max; i++)
    {
        if(f[i]==1)
        {
            printf("%d ",i);
            while(f[++i]==1);
            printf("%d\n",i);
        }
        else if(g[i]==1)
            printf("%d %d\n",i,i);
    }
    return 0;
}