#include <fstream>
using namespace std;

int trailing_zeros( int n ) {
	int result = 0;
	int power = 5;

	while( n / power >= 1 ) {
		result += n / power;
		power *= 5;
	}

	return result;
}

int solve( int p ) {
	int a = 0;
	int b = 5 * p;
	int c = -1;
	int zeros;

	while( a < b && a != c && b != c ) {
		c = ( b + a ) / 2;
		zeros = trailing_zeros( c );
		if( zeros == p ) return c;
		if( zeros > p ) b = c;
		else a = c;
	}

	return -1;
}

int main() {
	int p;

	fstream f( "fact.in", ios::in );
	f >> p;

	fstream g( "fact.out", ios::out );
	g << solve( p );

	return 0;
}