#include <fstream>

using namespace std;

const char InFile[]="fact.in";
const char OutFile[]="fact.out";
const long long MaxN=1LL<<35;

ifstream fin(InFile);
ofstream fout(OutFile);

long long N,sol;

inline long long legendre(long long a,long long p)
{
	long long p2=p;
	long long sol=0;
	while(p2<=a)
	{
		sol+=a/p2;
		p2*=p;
	}
	return sol;
}

int main()
{
	fin>>N;
	fin.close();
	
	long long step=1;
	long long first=0;
	for(;step<=MaxN;step<<=1);
	for(;step;step>>=1)
	{
		long long index=first+step;
		if(index<=MaxN)
		{
			long long x=legendre(index,5);
			if(x<N)
			{
				first=index;
			}
		}
	}
	++first;
	if(legendre(first,5)==N)
	{
		sol=first;
	}
	else
	{
		sol=-1;
	}
	fout<<sol;
	fout.close();
	return 0;
}