#include<iostream>

using namespace std;

bool isdigital(char c)
{
    if(c>='a'&&c<='z'||c>='A'&&c<='Z') return false;
    else return true;
}

bool istwo(char c)
{
    if(c=='.') return true;
    else return false;
} 

int main()
{
    int n;
    cin>>n;

    int cnt=0;
    double sum=0;

    while(n--)
    {
        string num;
        cin>>num;
        double x;

        bool success=true;
        for(int i=0;i<num.size();i++)
        {
            if(!isdigital(num[i]))
            {
                success =false;
                break;
            }
        }

        int count=0;
        for(int i=0;i<num.size();i++)
        {
            if(istwo(num[i]))
            {
                count++;
            }
        }
        if(count>1) success=false;

        x=stod(num);
        if(x<-1000||x>1000) success=false;
        int k=num.find(".");
        if(k!=-1&&num.size()-k>3) success=false; //存在小数点并且多余两位有效数字

        if(success) cnt++,sum+=x;
        else printf("ERROR: %s is not a legal number\n",num.c_str());
    }
    if(cnt>1) printf("The average of %d numbers is %.2lf\n",cnt,sum/cnt);
    else if(cnt==1) printf("The average of 1 number is %.2lf\n",sum);
    else printf("The average of 0 numbers is Undefined\n") ;

    return 0;
 }