#include <iostream>
#include <vector>
#include <algorithm>

#define INPUT_FROM_FILE (0) 
#if INPUT_FROM_FILE
#include <fstream>
#endif

int main(int argc, char **argv){
	double v = 0;

#if INPUT_FROM_FILE
	//std::ifstream ifs("test.txt");
	FILE *fp = fopen("test.txt", "r");
#endif

#if INPUT_FROM_FILE
	while(fscanf(fp, "%lf", &v) != EOF){
#else
	while(scanf("%lf", &v) != EOF){
#endif
		double y = 4.9 * pow(v / 9.8, 2.0);
		int N = (int)std::ceil(y / 5.0 + 1.0);

		std::cout << N << std::endl;
	}
	
	return 0;
}
