#include <stdio.h>
#include <cmath>
#include <algorithm>
#include <stack>
#include <queue>
#include <vector>
typedef long long int ll;
#define BIG_NUM 2000000000
using namespace std;

struct Info{
	int small,big;
};


int main(){

	Info info[6];
	int left,right;

	for(int i = 0; i < 6; i++){
		scanf("%d %d",&left,&right);

		if(left <= right){
			info[i].small = left;
			info[i].big = right;
		}else{
			info[i].small = right;
			info[i].big = left;
		}
	}

	for(int i = 1; i <= 5; i++){
		for(int k = 5; k >= i; k--){
			if((info[k].small < info[k-1].small) ||
					(info[k].small == info[k-1].small && info[k].big < info[k-1].big)){
				swap(info[k],info[k-1]);
			}
		}
	}

	if(info[0].small == info[1].small && info[0].big == info[1].big &&
			info[2].small == info[3].small && info[2].big == info[3].big &&
			info[4].small == info[5].small && info[4].big == info[5].big &&
			info[0].small == info[2].small ){
		//Do nothing
	}else{
		printf("no\n");
		return 0;
	}


	if(info[0].big > info[2].big){
		if(info[0].big == info[4].big && info[2].big == info[4].small){
			printf("yes\n");
		}else{
			printf("no\n");
		}
	}else{
		if(info[0].big == info[4].small && info[2].big == info[4].big){
			printf("yes\n");
		}else{
			printf("no\n");
		}
	}

    return 0;
}