#include <cstdio>
#include <ctime>

int main()
{
	FILE *in=fopen("fact.in", "r"), *out=fopen("fact.out", "w");
	int cifrez=0, nr=0, cinci=0, aux=0;
	fscanf(in, "%d", &cifrez);
	if (!cifrez) nr=1;
	while (cifrez>cinci)
	{
		nr+=5;
		cinci++;
		if (++aux==5)
		{
			aux=0;
			cinci++;
		}
	}
	fprintf(out, "%d", nr);
}