Update app.py

app.py

@@ -1000,7 +1000,7 @@ def ask_ai(problem: str, sympy_info: dict, history: list) -> str:
         resp = requests.post(
             "https://openrouter.ai/api/v1/chat/completions",
             headers={"Authorization": f"Bearer {key}", "Content-Type": "application/json"},
-            json={"model": "meta-llama/llama-3.3-70b-instruct:free",
+            json={"model": "model": "deepseek/deepseek-r1:free",
                   "messages": messages, "max_tokens": 2048, "temperature": 0.15},
             timeout=60
         )