POJ2680（动态规划，大数）

import java.util.*;
import java.math.*;

public class Main {

    public static void main(String[] args) {
        final int maxn = 1010;
        BigInteger fa[] = new BigInteger[maxn];
        BigInteger fb[] = new BigInteger[maxn];
        BigInteger TWO = BigInteger.valueOf(2);
        fa[0] = fb[0] = BigInteger.ZERO;
        for (int i = 1; i < maxn; i ++) {
            fa[i] = fa[i-1].add(fb[i-1]);
            fb[i] = fa[i-1].add(fb[i-1]).add(BigInteger.valueOf(i).mod(TWO));
        }
        int n;
        Scanner cin = new Scanner(System.in);
        while (cin.hasNext()) {
            n = cin.nextInt();
            System.out.println(fb[n-1]);
        }
    }
}

import sys
fa = [0] * 1010
fb = [0] * 1010
fa[0] = 0;
fb[0] = 0;
for i in range(1, 1010):
    fa[i] = fa[i-1] + fb[i-1]
    fb[i] = fa[i-1] + fb[i-1] + i % 2

for line in sys.stdin:
    n = int(line)
    print(fb[n-1])