#include <iostream>
#include <string>
#include <vector>
#include <cstdio>

using namespace std;

int main(void) { // read bim file from stdin; create exclude files + list of chr*chunk*
  int chr, bp; double genpos; string snpID, line;
  vector <int> bps;
  while (cin >> chr >> snpID >> genpos >> bp) {
    bps.push_back(bp);
    getline(cin, line); // get rid of rest of line
  }
  int M = bps.size();
  //cout << "chr" << chr << ": " << M << " variants in bim file" << endl;
  const int Mchunk = 50000, minOverlap = 5000;
  int chunks = 1, Mcovered = Mchunk;
  while (Mcovered < M) {
    chunks++;
    Mcovered += Mchunk-minOverlap;
  }
  vector <int> chunkStarts(chunks), chunkEnds(chunks);
  if (chunks==1) {
    chunkEnds[0] = M;
  }
  else {
    for (int c = 0; c < chunks; c++) {
      chunkStarts[c] = (Mchunk-minOverlap)*c - c*(Mcovered-M)/(chunks-1);
      chunkEnds[c] = chunkStarts[c] + Mchunk;
      printf("chr %2d chunk %d bpStart %9d bpEnd %9d\n", chr, c+1,
	     bps[chunkStarts[c]], bps[chunkEnds[c]-1]);
    }
  }
}