#include<stdio.h>
#include<math.h>
int t,x=0,cp,putere=0,baza,p,j;
FILE *f,*g;
int main ()
{

f=fopen("fact.in","r");
fscanf(f,"%d",&p);
g=fopen("fact.out","w");
if(p==0)fprintf(g,"%d",1);
	else{	while(cp!=p){x+=5;putere=0;baza=0;cp=0;
							do{baza*=5;putere++;}while(putere<=x);
							for(j=1;j<=putere;j++){cp=cp+x/pow(5,j);}}
				fprintf(g,"%d",x);}
fclose(f);
fclose(g);
return 0;

}