#include<fstream>
#include<iostream>
using namespace std;
long int n,p;
ifstream f("fact.in");
ofstream g("fact.out");

long int nrzero(long int x)
{long c=5;n5=0;
while(c<=x){n5+=(x/c);c*=5;}
	
	/*long int n5=0,p5=0;
if(x<5)return 0;
for(int i=5;i<=x;i+=5){p5=i;while(p5%5==0){n5++;p5=p5/5;}}*/
return n5;
}

long int versol(long int ls,long int ld)
{
while(ls<=ld){long int m=(ld+ls)/2;if(nrzero(ls)==p)return ls;
if(nrzero(m)<p)return versol(m,ld);
else return versol(ls+1,m);}
}

int main()
{f>>p;
g<<versol(1,2000000000);
f.close();
g.close();
return 0;}