#include<fstream>
using namespace std;
int main()
{long n=1,p,r=1;
ifstream f("factorial.in");
ofstream g("factorial.out");
f>>p;
if (p==0) r=2 ;
while (p!=0) { n=n*r*(r+1)*(r+2)*(r+3)*(r+4);
r=r+5;
while (n%5==0) {p=p-1; n=n/10;
}
}
g<<r-1;
f.close();
g.close();
return 0;
}