#include <stdio.h>
#include <stdint.h>

/// <summary>
/// 入力された数字を返す
/// </summary>
/// <returns></returns>
uint64_t ReadNum() {
	int negate = 0;
	char c = getchar();
	uint64_t num = 0;
	int numCnt = 0;
	while (c != '\n') {
		if (c == '-') {
			negate = 1;
		}
		else {
			num = num * 10 + c - '0';
		}

		c = getchar();
	}
	if (negate == 1) {
		num *= -1;
	}
	return num;
}


int main()
{
	uint64_t n = ReadNum();
	uint64_t sum = 0;
	printf("%llu\n",(n/2+n/30)*2);
}