#include <cstdio>

using namespace std;
int p,i=0,x=0;
int divz(int n)
{
    int k=0;
    while(n)
    {
            k+=n/5;
            n=n/5;
    }
    return k;
}

int cautbin(int p)
{
    int lo=1,hi=(1<<31)-1,m;
    while(lo<hi)
    {
                m=((long long)lo+hi)/2;
                if(divz(m)>=p)hi=m;
                                   else lo=m+1;
    }
    if(divz(hi)==p)return hi;
    return -1;
}


int main()
{ 
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d",&p);
    printf("%d\n",cautbin(p));
    return 0;  

}