#include<stdio.h>
FILE *f=fopen("fact.in","r");
FILE *g=fopen("fact.out","w");
int p,i,n,s,nr,ok;
int main()
{
fscanf(f,"%d",&p);
if(p==0) n=1;
else{ n=0;
      while(n<p) {  nr+=5;
                    s=nr;
		    while(s%5==0){ s/=5;n++;}
		    if(n>=p) ok=1;
		 }

      n=nr;
    }
if(ok=1) fprintf(g,"0");
else fprintf(g,"%d",n);
fclose(f);
fclose(g);
return 0;
}