#include <stdio.h>
#include <stdlib.h>

int main() {
	long n;
	scanf("%ld", &n);
	int width = 1;
	int current = 0;
	for (; n; --n) {
		++current;
		if (current == width) {
			current = 0;
			++width;
		}
	}
	printf("%d\n", width - 1);
}