#include <iostream>
#include <fstream>
using namespace std;
int main()
{int long long p,v=1,c=1,aux,a,s,i;
/*ifstream f("fact.in");
ofstream g("fact.out");
f>>p;*/
cin>>p;
while(v!=0)
{aux=1;
a=0;
s=0;
while (aux<=c)
{aux=aux*5;
a=a+1;}
a=a-1;
for(i=1;i<=a;i++)
{s=s+c/pow(5,i);}
if (s==p) v=0;
c=c+1;}
cout<<c-1;
/*g<<(c-1);
f.close();
g.close();*/
return 0;
}