#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;

char s[100];
int len;double x;

int check()
{
    for(int i=0;i<len;i++)
    {
        if(s[i]=='-'||s[i]=='.'||'0'<=s[i]&&s[i]<='9') continue;
        else return 0;
    }
    int p=find
 
(s,s+len,'.')-s;
    int p1=find(s+p+1,s+len,'.')-s;
    int p2=find(s,s+len,'-')-s;
    if(p2!=len&&p2!=0||p2==0&&len==1) return 0;
    if(p1!=len) return 0;
    if(len-1-p>2) return 0;
    sscanf(s,"%lf",&x);
    if(x<1e3+1e-8&&x>-1e3-1e-8) return 1;
    return 0;
}

int
 
 main()
{
    int n;scanf("%d",&n);
    double ans=0;
    int num=0;
    for(int i=1;i<=n;i++)
    {
        scanf("%s",s);
        len=strlen(s);
        if(check()) ans+=x,num++;
        else printf("ERROR: %s is not a legal number\n",s);
    }
    if(num>1) printf("The average of %d numbers is %.2lf\n"
 
,num,ans/num);
    else if(num==1) printf("The average of 1 number is %.2lf\n",ans);
    else puts("The average of 0 numbers is Undefined");
    return 0;
}