Etruscan Warriors Never Play Chess

A troop of Etruscan warriors is organized as follows. In the first row, there is only one warrior; then, the second row contains two warriors; the third row contains three warriors, and so on. In general, each row i contains i warriors.

We know the number of Etruscan warriors of a given troop. You have to compute the number of rows in which they are organized.

Please note that there may be some remaining warriors (this could happen if they are not enough to form the next row). For example, 3 warriors are organized in 2 rows. With 6 warriors you can form 3 rows; but you can also form 3 rows with 7, 8 or 9 warriors.