text: const fs = require('fs');
  const readline = require('readline');
  
  
  function readMtx(pth, a) {
    var input = fs.createReadStream(pth), n = 0;
    var reader = readline.createInterface({input});
    return new Promise(fres => {
      reader.on('line', l => {
        if (l.startsWith('%')) return;
        if (++n === 1) return;
        var [u, v] = l.split(/\s+/g).map(parseInt);;
        a.addEdge(u, v);
      });
      reader.on('close', fres);
    });
  }
  module.exports = readMtx;
  