#include<stdio.h>

int main()
{
    int a[101][101]={0} , i , j , count[101] , cc=0 , n , p[101][2]  , booll[101]={0} , k ,temp ,max, maxind;
    int t1, t2 ;
    scanf("%d",&n);        k=n;

    for( i = 0 ; i < n ; i++ )
    {
        scanf("%d %d",&p[i][0] , &p[i][1]);
        if( p[i][0] > p[i][1] ) {    temp = p[i][0] ; p[i][0] = p[i][1];    p[i][1] = temp;    }

        for( j = 0 ; j < i ; j++ )
        {
            if( ( p[i][0] > p[j][0] && p[i][0] < p[j][1] ) || ( p[i][1] > p[j][0] && p[i][1] < p[j][1] )
                || ( p[j][0] > p[i][0] && p[j][0] < p[i][1] ) || ( p[j][1] > p[i][0] && p[j][1] < p[i][1] ))
            {    a[i][j] = a[j][i] = 1;    count[i]++;    count[j]++;            }

        }

        booll[i]=1;
    }

    for( i = 0 ; i < n ; i++)
     if(count[i]) cc++;

    while( cc )
    {
        max = 0;    maxind = 0;
        for( i = 0 ; i < n ; i++ )
        if( count[i] > max && booll[i] ) {    max = count[i];     maxind = i;    }

        i = maxind;
        booll[i] = 0;    count[i]=0;        cc--;    k--;

        for( j = 0 ; j < n ; j++ )
        if( a[i][j] ){    a[i][j] = 0;    a[j][i] = 0;    count[j]--;        if(!count[j]) cc--;    }

    }

    for( i = 1 ; i < n ; i++ )
    {
            j=i-1;  temp = booll[i];    t1=p[i][0]  ; t2 = p[i][1];
            while( j >= 0  && t1 < p[j][0] )
            {   p[j+1][0] = p[j][0];    p[j+1][1] = p[j][1];    booll[j+1] = booll[j];      j--;    }

            p[j+1][0] = t1;     p[j+1][1]=t2;   booll[j+1] = temp;
    }

    printf("%d\n",k);
    for( i = 0 ; i < n ; i++ )
    if( booll[i] )    printf("%d %d\n", p[i][0] , p[i][1] );


    return 0;
}