水题三题：

1.给你B和N，求个整数A使得A^n最接近B

2. 输出第N个能被3或者5整除的数

3.给你整数n和k，让你求组合数c(n,k)

1.poj 3100 (zoj 2818) Root of the Problem:

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemCode=2818

http://poj.org/problem?id=3100

#include<cstdio>

#include<cmath>

int main()

{

	int b,n;

	while(~scanf("%d%d",&b,&n),b||n)

	{

		int a=pow(b,1.0/n);

		int ans=a;

		if(b-pow(ans,n) > pow(ans+1,n)-b)

			ans++;

		printf("%d\n",ans);

	}

	return 0;

}

2.ZOJ 2829 Beautiful Number

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=1829

#include<cstdio>

const int MAXN=300000;

int a[MAXN],len=1;

int main()

{

	for(int i=3;i<MAXN;i++)

		if(i % 3==0 || i %5==0)

			a[len++]=i;

	int n;

	while(~scanf("%d",&n))

	{

		printf("%d\n",a[n]);

	}

	return 0;

}

3.ZOJ 1938 Binomial Showdown (poj 2249)

http://poj.org/problem?id=2249

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=938

#include<cstdio>

typedef long long LL;

LL ans,n,k;

int main()

{

	while(scanf("%lld%lld",&n,&k),n)

	{

		ans=1;

		if(k == 0)

		{

			printf("1\n");

			continue;

		}

		if(k > n-k )k=n-k;

		for(int i=1;i<=k;i++)

		{

			ans=ans*(n-i+1)/i;

		}

		printf("%lld\n",ans);

	}

	return 0;

}