#include<stdio.h>
FILE*f=fopen("fact.in","r");
FILE*g=fopen("fact.out","w");
int n;
int main()
{
	fscanf(f,"%d",&n);
	
	int p=1;
	int u=5*n+1;
	int m;
	while(p<=u)
	{
		m=(p+u)/2;
		int put=5;
		int nr=0;
		while(put<=m)
		{
			nr+=m/put;
			put*=5;
		}
		if(nr>n)
			u=m-1;
		else if(nr<n)
			p=m+1;
		else
			break;
	}
	
	fprintf(g,"%d",m);
	
	
	
	fclose(f);
	return 0;
}