#include <bits/stdc++.h>
void swap(int *a, int *b) {
  int t = *a;
  *a = *b;
  *b = t;
}
void judge(int r[][2]) {
  int f = 1, i;
  for (i = 0; i < 6; i += 2) {
    if (r[i][0] != r[i + 1][0] || r[i][1] != r[i + 1][1]) {
      f = 0;
      break;
    }
  }
  puts(f ? "yes" : "no");
}
int main(void) {
  int r[6][2], i, j, t;
  for (i = 0; i < 6; i++) {
    scanf("%d %d", &r[i][0], &r[i][1]);
    if (r[i][0] > r[i][1]) swap(&r[i][0], &r[i][1]);
  }
  for (i = 0; i < 5; i++) {
    for (j = 5; j > i; j--) {
      if (r[j - 1][0] > r[j][0] ||
          (r[j - 1][0] == r[j][0] && r[j - 1][1] > r[j][1])) {
        swap(&r[j - 1][0], &r[j][0]);
        swap(&r[j - 1][1], &r[j][1]);
      }
    }
  }
  judge(r);
  return 0;
}
