A 3-year-old child has been delivered to a hospital with complaints of pain in the legs, fever, loss of appetite. Objectively: pale skin and mucosa, hemorrhagic rash. Lymph nodes are enlarged, painless, dense and elastic, not matted together. Bones, joints, and abdomen are painful. The liver and spleen are enlarged. Hemogram: Hb- 88 g/l, color index - 1,3, platelets - 80 × 109/l, leukocytes - 25,8 × 109/l, lymphoblasts - 70%, ESR - 52 mm/hour. Make the provisional diagnosis: