ISL 2007 C1

Let $n>1$ be an integer. Find all sequences $a_{1}, a_{2}, \ldots, a_{n^{2}+n}$ satisfying the following conditions: (a) $a_{i} \in\{0,1\}$ for all $1 \leq i \leq n^{2}+n$; (b) $a_{i+1}+a_{i+2}+\ldots+a_{i+n}<a_{i+n+1}+a_{i+n+2}+\ldots+a_{i+2 n}$ for all $0 \leq i \leq n^{2}-n$. (Serbia)