Problem Solving
Time Limit: 2000MS | | Memory Limit: 65536K |
Total Submissions: 1914 | | Accepted: 747 |
Description
In easier times, Farmer John's cows had no problems. These days, though, they have problems, lots of problems; they have P (1 ≤ P ≤ 300) problems, to be exact. They have quit providing milk and have taken regular jobs like all other good citizens. In fact, on a normal month they make M (1 ≤ M ≤ 1000) money.
Their problems, however, are so complex they must hire consultants to solve them. Consultants are not free, but they are competent: consultants can solve any problem in a single month. Each consultant demands two payments: one in advance (1 ≤ payment ≤ M) to be paid at the start of the month problem-solving is commenced and one more payment at the start of the month after the problem is solved (1 ≤ payment ≤ M). Thus, each month the cows can spend the money earned during the previous month to pay for consultants. Cows are spendthrifts: they can never save any money from month-to-month; money not used is wasted on cow candy.
Since the problems to be solved depend on each other, they must be solved mostly in order. For example, problem 3 must be solved before problem 4 or during the same month as problem 4.
Determine the number of months it takes to solve all of the cows' problems and pay for the solutions.
Input
Line 1: Two space-separated integers:
M and
P.
Lines 2..
P+1: Line
i+1 describes problem
i with two space-separated integers:
Bi and
Ai.
Bi is the payment to the consult BEFORE the problem is solved;
Ai is the payment to the consult AFTER the problem is solved.
Output
Line 1: The number of months it takes to solve and pay for all the cows' problems.
Sample Input
100 5 40 20 60 20 30 50 30 50 40 40
Sample Output
6
Hint
+------+-------+--------+---------+---------+--------+ | | Avail | Probs | Before | After | Candy | |Month | Money | Solved | Payment | Payment | Money | +------+-------+--------+---------+---------+--------+ | 1 | 0 | -none- | 0 | 0 | 0 | | 2 | 100 | 1, 2 | 40+60 | 0 | 0 | | 3 | 100 | 3, 4 | 30+30 | 20+20 | 0 | | 4 | 100 | -none- | 0 | 50+50 | 0 | | 5 | 100 | 5 | 40 | 0 | 60 | | 6 | 100 | -none- | 0 | 40 | 60 | +------+-------+--------+---------+---------+--------+
Source
算法分析
代码实现: