In c++

Speed Limit Bill and Ted are taking a road trip. But the odometer in their car is broken, so they don't know how many miles they have driven. Fortunately, Bill has a working stopwatch, so they can record their speed and the total time they have driven. Unfortunately, their record keeping strategy is a little odd, so they need help computing the total distance driven. You are to write a program to do this computation. For example, if their log shows Speed in miles per hour | Total elapsed time in hours ||20|2||30|6||10|7|| this means they drove 2 hours at 20 miles per hour, then 6-2=4 hours at 30 miles per hour, then 7-6=1 hour at 10 miles per hour. The distance driven is then (2) (20) + (4) (30 + (1) (10) = 40 + 120 + 10 = 170 miles. Note that the total elapsed time is always since the beginning of the trip, not since the previous entry in their log. Input: The input consists of one or more data sets. Each set starts with a line containing an integer n, 1sns 10, followed by n pairs of values, one pair per line. The first value in a pair, s, is the speed in miles per hour and the second value, t, is the total elapsed time. Both s and t are integers, 1 sss 90 and 1sts 12. The values for t are always in strictly increasing order. A value of -1 for n signals the end of the input. Output: For each input set, print the distance driven, followed by a space, followed by the word "miles". Example input: 202 306 107 601 305 151 252 303 105 Example output: 170 miles 180 miles 90 miles Calculate the following inputs by hand to make sure your solution is correct. 3 50 2 253 356 2 102 204