#include <cstdio>
#include <iostream>
using namespace std;
int nr_zero(int n)
{
    int nr=0;
    while(n>0)
    {
        nr=nr+n/5;
        n/=5;
    }
    return nr;
}
int caut_bin(int p)
{
    long long dr=500000001,st=1,mij,ans;
    while(st<=dr)
    {
        mij=(st+dr)/2;
        int aux=nr_zero(mij);
        if (p>aux)
            st=mij+1;
        else if (p<=aux)
        {
            dr=mij-1;
            if (p==aux)
                ans=mij;
        }
    }
    return ans;
}
int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    int p;
    scanf("%d",&p);
    cout<<caut_bin(p);

    return 0;
}