#include<stdio.h>
int p,n;
void citire(){
   freopen("fact.in","r",stdin);
   scanf("%d",&p);
}
int rezolvare(){
     if(p==0)
       return 1;
     p-=1;
     if(p<10)
       return p*5;
     else{
       for(int i=5;i<p/5;i*=5)
         p-=i;
       return p*5;       
     }
     return -1;
}
void afisare(){
     freopen("fact.out","w",stdout);
     printf("%d",rezolvare());
     fclose(stdout);
}
int main(){
    citire();
    afisare();
    return 0;
}