#include<stdio.h>
int main()
{long i,r,kmax,p,nrsol=0,nr0=25;
FILE *f=fopen("fact.in","r");
FILE *g=fopen("fact.out","w");
i=5;
kmax=25;
r=1;
fscanf(f,"%ld",&p);
if (p==0) fprintf(g,"1");
else
{while (nrsol<=p)
	{if (i%kmax==0) {r++; nrsol+=r; kmax=kmax*5;}
	else if (nr0==i) {nr0=nr0+25; nrsol++;}
	 else nrsol++;
	 i+=5;}
  fprintf(g,"%ld",i-10);   }
fclose(f);
fclose(g);
return 0;
}