#include<iostream.h>
#include<math.h>

void main()
{
    int n,a[20];
    int temp;
    signed int t;
    cin>>n;
    for(int i=0;i<n;i++)cin>>a[i];
    for(int k=0;k<n-1;k++){
        for(int m=k+1;m<n;m++){
            if(a[m]>a[k]){
            temp=a[m];
            a[m]=a[k];
            a[k]=temp;
            }
        }
    }
    t=a[0];
    for(int k1=1;k1<n;k1++){
        if(t>0)t-=a[k1];
        else t+=a[k1];
    }
    cout<<abs(t)<<endl;
}

Try this test
7
5 6 8 2 6 7 8

Right answer is 0 (first 4 and last 3) but your program write 2