#include<fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int kkt(long n){
    int k=5,s=0;
    while(k<=n){s+=n/k;k*=5;}
    return s;
}
int main()
{
int st=1,dr=200000000,p,m=1,nr,a,mij;
f>>p;
if(p==0) g<<1;
else
{
    while(st<=dr&&m)
    {
        mij=(st+dr)/2;
        a=kkt(mij);
        if(a==p){nr=mij-mij%5;m=0;}
        else
            if(a<p) st=mij+1;
                else dr=mij-1;
        }
    g<<nr;
}
return 0;
}