#include <cstdio>
using namespace std;
int p,lg=134217728;

int zero(int x)
{
    int s=0;
    while(x/5 != 0)
    {
        s+=(x/5);
        x/=5;
    }
    return s;
}
int cautbin()
{
    int i;
    for(lg, i=100000000;lg;lg>>=1)
        if(i - lg >0 && zero(i - lg) >= p)
            i-=lg;
    return i;
}
int main()
{
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);
    scanf("%d", &p);

    printf("%d", cautbin());

    return 0;
}