#include<fstream>
#include<iostream>
using namespace std;
long int n,p,b;
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;}
return n5;
}

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

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