Row with balanced signs

You are given an $m \times n$ matrix. Find the number of the first row that has as many positive elements as negative ones (rows are numbered from $1$). Zeros do not count: a row of zeros only qualifies too ($0 = 0$). If there is no such row — $0$.

The first line contains $m$ and $n$ ($1 \le m, n \le 100$). Each of the next $m$ lines contains $n$ integers ($|a_{ij}| \le 10^9$).

A single integer — the row number or $0$.

For each row keep two counters (or one: $+1$ for a positive, $-1$ for a negative). Stop at the first match. In the first example row 1 has two negatives and one positive, row 2 has one of each: the answer is $2$.