I tried but faild
hmm.. this problem is LCS????
please change this source correctly..
my source is

#include <stdio.h>

int n, m;

int a[505];
int b[505];

int dy[505][505];
int check[505][505];

void input()
{
	int i;
	scanf("%d", &n);
	for(i=1;i<=n;i++)
	{
		scanf("%d", &a[i]);
	}
	scanf("%d", &m);
	for(i=1;i<=m;i++)
	{
		scanf("%d", &b[i]);
	}
}

void back(int x, int y, int cnt)
{
	int i;
	if(x==0 || y==0)
	{
		return;
	}
	if(a[x]==b[y])
	{
		back(x-1, y-1, cnt+1);
		printf("%d ", a[x]);
	}
	else if(dy[x-1][y]>dy[x][y-1])
	{
		back(x-1, y, cnt);
	}
	else
	{
		back(x, y-1, cnt);
	}
}

void process()
{
	int i, j;
	for(i=1;i<=n;i++)
	{
		for(j=1;j<=m;j++)
		{
			if(a[i]==b[j] && a[i]>check[i-1][j-1])
			{
				dy[i][j]=dy[i-1][j-1]+1;
				check[i][j]=a[i];
			}
			else
			{
				if(dy[i-1][j]>dy[i][j-1])
				{
					dy[i][j]=dy[i-1][j];
					check[i][j]=check[i-1][j];
				}
				else
				{
					dy[i][j]=dy[i][j-1];
					check[i][j]=check[i][j-1];
				}
			}
		}
	}
	printf("%d\n", dy[n][m]);
	back(n, m, 0);
}

int main()
{
	input();
	process();
	return 0;
}