#include <iostream>
#include <fstream>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
inline long long nr0(int n)
{
    if(n==0)
        return 1;
    long long nr=0;
    while(n>0)
    {
        nr=nr+n/5;
        n=n/5;
    }
    return nr;
}
inline int caut_bin(int p)
{
    long long st=0;
    long long dr=410000000;
    long long mij=(st+dr)/2;
    while(st<=dr)
    {
        mij=(st+dr)/2;
        if(nr0(mij)<p)
            st=mij+1;
        else if(nr0(mij)>p)
            dr=mij;
        else
            break;
    }
    while(nr0(mij)==p)
        mij--;
    mij++;
    return mij;
}
int main()
{
    int p;
    in>>p;
    out<<caut_bin(p);
    cerr<<caut_bin(100000000);
    return 0;
}