Handcrafted Gift

Adam is making Bob a hand-crafted necklace as a gift. A necklace consists of $n$ beads, numbered $0$ to $n-1$ from left to right. Each bead can either be red or blue in colour. Bob has sent Adam a list of $r$ requirements for the necklace. The $i$th requirement ($0 \leq i \lt r$) states that the beads from positions $a\[i]$ to $b\[i]$ inclusive should have $x\[i]$ unique colours. 

Help Adam find a possible configuration of beads that satisfies all of Bob's requirements, or determine that it is impossible.

• $1 \leq n, r \leq 500\\;000$
• $0 \leq a\[i] \leq b\[i] \leq n-1$ (for all $0 \leq i \leq n-1$)
• $1 \leq x\[i] \leq 2$ (for all $0 \leq i \leq n-1$)