#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
long long  p,x,i,j,k,nr;
int main()
{
    fin>>p;
    if(p==0)
        fout<<1;
    else
    {
        i=5;
        while(k==0)
        {
            nr=0;
            for(j=1;j<=i;j++)
            {
                x=j;
                while(x%5==0)
                {
                    x/=5;
                    nr++;
                }
            }
            i+=5;
            if(nr>=p) k=1;
        }
    }
    fout<<i-5;
    return 0;
}