>>245
#include <iostream>
#include <algorithm>
#include <iterator>
#include <numeric>
#include <fstream>

using namespace std;

struct data {char name [10]; int val;} da[10];

data operator+ (const data& lhs, const data& rhs)
{ data result; result.val = lhs.val, result.val += rhs.val; return result; }
istream& operator>>(istream& is, data& d) { is >> d.name >> d.val; return is; }

int main()
{
  ifstream fin("data.txt");
  data *p = copy(istream_iterator<data>(fin), istream_iterator<data>(), da);
  data d = {0};
  cout << (double)accumulate(da, p, d).val / (p - da) << endl;
}