#include <bits/stdc++.h>   using std::cin;   using std::cout;   using std::fixed;   using std::make_pair;   using std::max;   using std::min;   using std::pair;   using std::set;   using std::sort;   const long long base = (long long)(5 * 1e8 + 5);   const long long coefficient = (long long)(4 * 1e9);   long long convertCoordinate(long long x, long long y) {     return (x + base) * coefficient + (y + base);   }   pair<long long, long long> convertCoordinateBack(long long pos) {     long long x = pos / coefficient - base - base;     long long y = pos % coefficient - base - base;     return make_pair(x, y);   }   const int MaxN = 200000 + 9;   int n, k, l, r, used;   long long points[MaxN];   long long x, y, now;   set<long long> waitList;   set<pair<long long, long long> > ans;   set<long long>::iterator it;   set<pair<long long, long long> >::iterator pit;   int main() {     waitList.clear();     ans.clear();     scanf( %d%d , &n, &k);     if (k >= n) return cout <<  -1 n , 0;     for (int i = 1; i <= n; i++) {       scanf( %I64d%I64d , &x, &y);       points[i] = convertCoordinate(x, y);     }     sort(points + 1, points + n + 1);     for (int i = 1; i <= min(k + 2, n); i++) {       for (int j = max(n - k - 2, 1); j <= n; j++) {         waitList.insert(points[i] + points[j]);       }     }     for (it = waitList.begin(); it != waitList.end(); it++) {       l = 1;       r = n;       used = 0;       while (l <= r) {         now = points[l] + points[r];         if (now < (*it))           l++, used++;         else if (now > (*it))           r--, used++;         else           l++, r--;       }       if (used <= k) ans.insert(convertCoordinateBack(*it));     }     if (ans.size() == 0)       printf( 0 n );     else {       printf( %d n , ans.size());       for (pit = ans.begin(); pit != ans.end(); pit++) {         printf( %.2lf %.2lf n , (double)(*pit).first * 0.5,                (double)(*pit).second * 0.5);       }     }   }   