#include<fstream>

using namespace std;
long int n,p;
ifstream f("fact.in");
ofstream g("fact.out");

long int nrzero(long int x)
{long int n2=0,n5=0,p2=0,p5=0;
if(x<5)return 0;
for(int i=2;i<=x;i+=2){p2=i;while(p2%2==0){n2++;p2=p2/2;}}
for(int i=5;i<=x;i+=5){p5=i;while(p5%5==0){n5++;p5=p5/5;}}
if(n2<n5)return n2;
else return n5;
}

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

int main()
{f>>p;
g<<versol(1,5000000);
f.close();
g.close();
return 0;}