#include <iostream>
#include <vector>
using namespace std;
int am_dig(int k){
int res = 0;
while(k > 0){
res++;
k /= 10;
}
return res;
}
double average(vector<double> a){
double sum = 0;
for(auto i: a)
sum += i;
return sum/a.size();
}
int main() {
vector<double> a;
double x = 1;
while(x != 0){
cin >> x;
if(am_dig(x) == 3)
a.push_back(x);
}
if(a.size() == 0)
cout << "NO";
else
cout << average(a);
}
var a:array[1..10,1..10]of integer;
i,j:integer;
begin
for i:=2 to 10 do a[i,1]:=i-1;
for i:=2 to 10 do a[1,i]:=i-1;
for i:=2 to 10 do
for j:=2 to 10 do
a[i,j]:=a[i,1]*a[1,j];
for i:=1 to 10 do begin
for j:=1 to 10 do
write(a[i,j]:3); if j=10 then writeln; end;
end.