using System;
class Program
{
static int sqrt_(int n) {
if (n == 0 || n == 1)
return n;
int i = 1, sq = 1;
while (sq <= n) {
i++;
sq = i * i;
}
return i - 1;
}
static void Main()
{
Console.WriteLine(sqrt_(9));
Console.WriteLine(sqrt_(5));
Console.WriteLine(sqrt_(26));
Console.WriteLine(sqrt_(16));
}
}
/*
run:
3
2
5
4
*/