Definition: Given a math word problem, answer the following question. You might need to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the question and then only report the final numerical answer.
Input: it is 78 miles to grandma 's house . mr. welch drove 35 miles . he stopped to buy a pie for dessert . then he drove 18 miles and stopped to put gas in the car . how many more miles until he reaches grandma 's house ?
Output:
25