define(['lib/leaflet/dist/leaflet-src'], function(L) {
    var map = L.map(document.body).setView({lat: 55.7529120574368, lng: 37.622079849243164}, 12);

    L.tileLayer('http://{s}.tile.osm.org/{z}/{x}/{y}.png', {
        attribution: '&copy; <a href="http://osm.org/copyright">OpenStreetMap</a> contributors'
    }).addTo(map);

    return map;
});
define(['lib/leaflet/dist/leaflet-src'], function(L) {
    var map = L.map(document.body).setView({
        lat: 55.7529120574368,
        lng: 37.622079849243164
    }, 12);

    var tl = L.tileLayer('http://stamen-tiles-{s}.a.ssl.fastly.net/toner/{z}/{x}/{y}.png', {
        attribution: 'Map tiles by <a href="http://stamen.com">Stamen Design</a>, <a href="http://creativecommons.org/licenses/by/3.0">CC BY 3.0</a> &mdash; Map data &copy; <a href="http://www.openstreetmap.org/copyright">OpenStreetMap</a>',
        subdomains: 'abcd',
        minZoom: 0,
        maxZoom: 20,
        ext: 'png'
    });

    tl.addTo(map);

    return map;
});
use Stamen's toner base layer