https://codeforces.com/contest/1087/problem/C

题解：有点曼哈顿距离的感觉

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=1000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,q;
set<pair<int, int> > sen;
int x_s[3], y_s[3];
int xA, yA, xB, yB, xC, yC;
void walk(int xx, int yy, int xt, int yt) {
	while(xx < xt) {
		xx++;
		sen.insert(make_pair(xx, yy));
	}
	while(xx > xt) {
		xx--;
		sen.insert(make_pair(xx, yy));
	}
	while(yy < yt) {
		yy++;
		sen.insert(make_pair(xx, yy));
	}
	while(yy > yt) {
		yy--;
		sen.insert(make_pair(xx, yy));
	}
}
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    //scanf("%d",&n);
	scanf("%d%d%d%d%d%d", x_s, y_s, x_s+1, y_s+1, x_s+2, y_s+2);
	xA = x_s[0];
	yA = y_s[0];
	xB = x_s[1];
	yB = y_s[1];
	xC = x_s[2];
	yC = y_s[2];
	for(int i = 0; i < 3; i++) {
		sen.insert(make_pair(x_s[i], y_s[i]));
	}
	sort(x_s, x_s+3);
	sort(y_s, y_s+3);
	walk(xA, yA, x_s[1], y_s[1]);
	walk(xB, yB, x_s[1], y_s[1]);
	walk(xC, yC, x_s[1], y_s[1]);
	printf("%d\n", (int)sen.size());
	for(pair<int, int> p : sen) {
		printf("%d %d\n", p.first, p.second);
	}
    //cout << "Hello world!" << endl;
    return 0;
}