#include<stdio.h>
#include<math.h>

int main()
{
	unsigned long long i=1,buff;
	int cifre=0,nr;
	FILE *in,*out;
	
	in=fopen("fact.in","r");
	out=fopen("fact.out","w");
	
	fscanf(in,"%d",&nr);
	printf("nr este:%d",nr);
	
	while(cifre<nr)
	{
		/*if(cifre>nr)
		{
			fprintf(out,"-1");
			exit(1);
		}*/
			
		buff=i;				
		while(buff%10==0)
		{	
			cifre++;
			buff=buff/10;
		}	
//printf("merge\n");		
		while(buff%5==0)
		{
			cifre++;
			buff=buff/5;
		}		
		//printf("i:%d zerouri:%d\n",i,cifre);
		i++;
	}
	
	fprintf(out,"%d",i-1);
	return 0;




}