Time Limit: 2 Seconds
Memory Limit: 65536 KB
In Pearlania everybody is fond of pearls. One company, called The Royal Pearl,
produces a lot of jewelry with pearls in it. The Royal Pearl has its name because
it delivers to the royal family of Pearlania. But it also produces bracelets
and necklaces for ordinary people. Of course the quality of the pearls for these
people is much lower then the quality of pearls for the royal family. In Pearlania
pearls are separated into 100 different quality classes. A quality class is
identified by the price for one single pearl in that quality class. This price
is unique for that quality class and the price is always higher then the price
for a pearl in a lower quality class.
Every month the stock manager of The Royal Pearl prepares a list with the number
of pearls needed in each quality class. The pearls are bought on the local pearl
market. Each quality class has its own price per pearl, but for every complete
deal in a certain quality class one has to pay an extra amount of money equal
to ten pearls in that class. This is to prevent tourists from buying just one
Also The Royal Pearl is suffering from the slow-down of the global economy.
Therefore the company needs to be more efficient. The CFO (chief financial officer)
has discovered that he can sometimes save money by buying pearls in a higher
quality class than is actually needed. No customer will blame The Royal Pearl
for putting better pearls in the bracelets, as long as the prices remain the
For example 5 pearls are needed in the 10 Euro category and 100 pearls are needed
in the 20 Euro category. That will normally cost: (5+10)*10 + (100+10)*20 =
Buying all 105 pearls in the 20 Euro category only costs: (5+100+10)*20 = 2300
The problem is that it requires a lot of computing work before the CFO knows
how many pearls can best be bought in a higher quality class. You are asked
to help The Royal Pearl with a computer program.
Given a list with the number of pearls and the price per pearl in different
quality classes, give the lowest possible price needed to buy everything on
the list. Pearls can be bought in the requested, or in a higher quality class,
but not in a lower one.
The first line of the input contains the number of test cases. Each test case
starts with a line containing the number of categories c (1 <= c <= 100).
Then, c lines follow, each with two numbers ai and pi. The first of these numbers
is the number of pearls ai needed in a class (1 <= ai <= 1000). The second
number is the price per pearl pi in that class (1 <= pi <= 1000). The
qualities of the classes (and so the prices) are given in ascending order. All
numbers in the input are integers.
For each test case a single line containing a single number: the lowest possible
price needed to buy everything on the list.
Source: Northwestern Europe 2002