You are given a math word problem and you are supposed to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the following question and then only report the final numerical answer.

Input: Consider Input: A waiter at ' The Greasy Spoon ' restaurant had 29 customers to wait on . During the lunch rush he added another 20 customers . If 34 of the customers did n't leave him a tip , how many customers did leave a tip ?

Output: 15


Input: Consider Input: Joan has 47 green and 48 red marbles . Fred took 24 of Joan 's green marbles . How many green marbles does Joan now have ?

Output: 23


Input: Consider Input: Jason has 7 violet balloons and 4 red balloons . He lost 3 of the violet balloons . How many violet balloons does Jason have now ?


Output: 4