#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
long long na,b,c,a,m,P,i;
int main()
{ f>>P;
na=1;
if (P==0) g<<1;
else    {if (P>=1000000){na=4000004;c=999999;}
 for (i=na;c!=P;i++)  {m=i;
 while (m%2==0) {a++;m=m/2;}
 while (m%5==0) {b++;m=m/5;}
while (a&&b) {a--;b--;c++;}
}}
g << i-1;
    return 0;
}