#include <fstream>

using namespace std;
ifstream fin ("factorial.in");
ofstream fout ("factorial.out");
int p,st,dr,mid,i,a,x;
int main()
{
    fin>>p;

    st=1;
    dr=1000000000;
    mid=(st+dr)/2;
    while(st<=dr)
    {

        a=0;
        for(i=5;i<=mid;i+=5)
        {
            x=i;
            while(x%5==0 && x!=0)
            {
                a++;
                x=x/5;
            }
        }

        if(a<p)
        {
            st=mid+1;
            mid=(st+dr)/2;
        }

        if(a>=p)
        {
            dr=mid-1;
            mid=(st+dr)/2;
        }
    }
    fout<<st;

    return 0;
}