# BZOJ 1655: [Usaco2006 Jan] Dollar Dayz 奶牛商店 (母函数，高精度)

## 1655: [Usaco2006 Jan] Dollar Dayz 奶牛商店

Time Limit: 5 Sec  Memory Limit: 64 MB
Submit: 353  Solved: 190
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## Description

Farmer John goes to Dollar Days at The Cow Store and discovers an unlimited number of tools on sale. During his first visit, the tools are selling variously for \$1, \$2, and \$3. Farmer John has exactly \$5 to spend. He can buy 5 tools at \$1 each or 1 tool at \$3 and an additional 1 tool at \$2. Of course, there are other combinations for a total of 5 different ways FJ can spend all his money on tools. Here they are: 1 @ US\$3 + 1 @ US\$2 1 @ US\$3 + 2 @ US\$1 1 @ US\$2 + 3 @ US\$1 2 @ US\$2 + 1 @ US\$1 5 @ US\$1 Write a program than will compute the number of ways FJ can spend N dollars (1 <= N <= 1000) at The Cow Store for tools on sale with a cost of \$1..\$K (1 <= K <= 100).

约翰到奶牛商场里买工具．商场里有K(1≤K≤100).种工具，价格分别为1，2，…，K美元．约翰手里有N(1≤N≤1000)美元，必须花完．那他有多少种购买的组合呢？

## Input

A single line with two space-separated integers: N and K.

仅一行，输入N，K.

## Output

A single line with a single integer that is the number of unique ways FJ can spend his money.

不同的购买组合数．

5 3

5

## 作者： CrazyKK

ex-ACMer@hust，researcher@sensetime