#include<stdio.h>
main()
{
long long n=1000000000;
long long p,i,k,j,s,sp,valid,x;
FILE *f,*g;
f=fopen("fact.in","r");
g=fopen("fact.out","w");
fscanf(f,"%lld",&p);
valid=0;
if(p==0)fprintf(g,"%lld",1);
else
{
 i=1;
 do{
    k=(n+i)/2;
    s=0;
    sp=5;
    do{
	s+=k/sp;
	x=k/sp;
	sp*=5;
       }while(x>0);
    if(s==p)valid=1;
    else
     { if(s>p) n=k;
       else i=k;
     }

 }while(valid!=1);
 k/=5;k*=5;
 if(valid==1)fprintf(g,"%lld",k);
 else fprintf(g,"%lld",-1);
 }

fclose(f);
fclose(g);
return 0;
}