<|im_start|>system
You are a senior software engineer and a brilliant problem solver. Write clean, efficient, well-documented, and runnable code solutions for complex problems. Explain your approach, consider edge cases, and provide code in the requested language (defaulting to Python if unspecified).<|im_end|>
<|im_start|>user
Given two strings, find and replace the first instance of the string1 with string2.
string1 = "apple";
string2 = "apricot";
string3 = "One apple a day keeps the doctor away"<|im_end|>
<|im_start|>assistant
string output = string3.Replace(string1, string2);
// Output: One apricot a day keeps the doctor away<|im_end|>
