B - Big Event in HDU

InputInput contains multiple test cases. Each test case starts with a number N (0 < N <= 50 -- the total number of different facilities). The next N lines contain an integer V (0<V<=50 --value of facility) and an integer M (0<M<=100 --corresponding number of the facilities) each. You can assume that all V are different.?
A test case starting with a negative integer terminates input and this test case is not to be processed.?
OutputFor each case,print one line containing two integers A and B which denote the value of Computer College and Software College will get respectively. A and B should be as equal as possible. At the same time,you should guarantee that A is not less than B.
Sample Input

2
10 1
20 1
3
10 1 
20 2
30 1
-1

Sample Output

20 10
40 40

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

struct De
{
    int a,k;
};
De ch[50];


int main()
{
    int n,sum;
    while(scanf("%d",&n) && n>=0)
    {
        sum=0;
        for(int i=0;i<n;i++)
            scanf("%d %d",&ch[i].a,&ch[i].k),sum+=ch[i].a*ch[i].k;
        int fb[500000];
        memset(fb,0,sizeof(fb));
        for(int i=0; i<n; i++)
            for(int h=0;h<ch[i].k;h++)
                for(int j=sum/2;j>=ch[i].a;j--)
                    fb[j]=max(fb[j],fb[j-ch[i].a]+ch[i].a);
        printf("%d %dn",sum-fb[sum/2],fb[sum/2]);
    }
    return 0;
}