#include <cstdio>

using namespace std;

int n, nr, i;

int main()
{
    freopen("factorial.in", "r", stdin);
    freopen("factorial.out", "w", stdout);

    scanf("%d", &n);
    while(nr<n)
    {
        i++;
        nr++;
        if(i%5==0)
            nr++;
    }
    if(i!=0)
        printf("%d", 5*i);
    else
        printf("1");
    return 0;
}