#include<stdio.h>
FILE *f1,*f2;
int main()
{long int x,p,nrad,nrp;
f1=fopen("fact.in","r");
fscanf(f1,"%li",&p);
fclose(f1);
if(p==0)
x=1;
else{
nrad=0;nrp=p-p%5;
while (nrp>=5){
nrad+=5;nrp-=5;
x=nrad;
while(x%5==0)
{x=x/5;nrp--;}
}
if(nrp<0)
x=-1;
else{
nrad=nrad+p%5+nrp;
x=nrad*5;}}
f2=fopen("fact.out","w");
fprintf(f2,"%li",x);
fclose(f2);
return 0;
}