025_a_2.js

var lines     = [];
var readline  = require('readline').createInterface(process.stdin, process.stdout);

readline.on('line', function(line) {
  lines.push(line);
  if(lines.length === 2) {
    var chars = , index = lines[1] - 1;
    console.log(chars[Math.floor(index / 5)] + chars[index % 5]);
    process.exit(0);
  }
});