How to solve the following error: User memory limit exceeded in Google Earth Engine?

Good morning,

I'm trying to do a supervised classification in Google Earth Engine and I come across the following error:

  

"User memory limit exceeded".

Does anyone know how to solve this problem?

Thank you

Follow the code:

Map.setCenter(-49.23728942871094,-16.651641716433563, 6);
var OLI = ee.ImageCollection('LANDSAT/LC08/C01/T1_RT_TOA')
    .filterBounds(geometry)
    //.filterMetadata('CLOUD_COVER', 'Less_Than', 0.3)
    //.filterDate('2018-01-01', '2018-12-31');
    .median();

var img = OLI;      

var amostra = veg.merge(agua).merge(solo);
var bandas = ['B4', 'B5', 'B6'];

var treino = img.select(bandas).sampleRegions ({
  collection:amostra,
  properties: ['class'],
  scale: 30
});

var classificacao = ee.Classifier.minimumDistance('euclidean').train({
  features: treino, 
  classProperty: 'class',
  inputProperties: bandas
}); 

var classificacao = img.select(bandas).classify(classificacao)

Map.addLayer(img, {bands: 'B6,B5,B4'});
Map.addLayer(classificacao, {min: 0, max: 2, palette:['green', 'blue', 'magenta']},'classificação');