#include<stdio.h>

int main()
{FILE*f,*g;
f=fopen("fact.in","r");
g=fopen("fact.out","w");
long p,n=1,i,k=0;
fscanf(f,"%ld",&p);

if(!p) {fprintf(g,"1");
	return 0;
	}
long t=2000000000;
for(i=1;i<=t;i++)
{n=n*i;    

while(n%10==0&&n)
{n=n/10;
k++;
		if(k==p)
	{fprintf(g,"%ld",i);return 0;}
		if(k>p)
	{fprintf(g,"1"); return 1;}
  }  n=n%10;
 }
return 0;

}