#include<iostream>
#include<fstream>
using namespace std;
int p,counter;
long long i;
int main()
{
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    fin>>p;
    for(i=1;i<=100000000;++i)
    {
        int fn=i;
        while(fn!=0)
        {
            if(fn%5==0)counter++;
            fn/=5;
        }
        if(counter==p)fout<<i;break;
    }
}