#include <stdio.h>

// nr natural minim pt care N! are P zerouri;

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

    int long p;
    scanf("%ld", &p);
    
    if(p <= 0)
    {
        printf("-1");
        return 0;
    }
    if(p <= 2)
    {
        printf("%ld", p*5);
        return 0;
    }
    printf("%ld", (p-1)*5);
    return 0;
}