#include <fstream>
#include<climits>
#define Maxim INT_MAX
using namespace std;
long long p;
long long NrZeroes(long long x)
{
    long long putere=5,suma=0;
    while(putere<=x)
        {suma+=x/putere;putere*=5;}
    return suma;
}
long long cautbin(long long left,long long right,long long val)
{
    long long st=left,dr=right,LastApp=-1;
    while(st<=dr)
        {
            long long mij=(dr-st)/2+st;
            long long fct=NrZeroes(mij);
            if(fct<p){st=mij+1;continue;}
            if(fct>p){dr=mij-1;continue;}
            LastApp=mij;
            dr=mij-1;
        }
    return LastApp;
}
int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>p;
    g<<cautbin(1,Maxim,p)<<'\n';
    return 0;
}