#include <stdio.h>

int main()
{
    int n;
	scanf("%d",&n);
	int i = 1, ans = 0, delta=1, cnt = 0;
	while (i<=n)
	{
		ans++;
		i+=delta;
		cnt++;
		if (cnt==2)
			delta++,cnt=0;
	}
	printf("%d\n", ans);
		
}