atcoderでwaが出る原因

#include <bits/stdc++.h>
using namespace std;
typedef long long lint;
#define rep(i, n) for(int i = 0; i < (int) n; i++)

int main(void)
{
    lint n;
    cin >> n;
    vector<lint> a(n);
    rep(i, n) cin >> a[i];
    const lint num = pow(10, 8);
    int ans = 0;
    rep(i, n) ans += a[i];
    ans = (n -1) * ans;
    sort(a.begin(), a.end());
    int result = 0;
    vector<lint> r(n);
    for(int i = 0; i < n; i++)
    {
        if(i == 0) r[i] = n - 1;
        else r[i] = r[i - 1];
        while(true)
        {
            if(a[i] + a[r[i]] < num)
            {
                break;
            }
            else if(r[i] >= 0)
            {
                r[i]--;
            }
            else
            {
                break;
            }
        }
    }
    for(int i = 0; i < n; i++)
    {
        if(r[i] + 1 > i) result += (n - r[i] - 1);
        else result += (n - r[i] - 2);
    }
    result /= 2;
    cout << ans - result* num << endl;
    return 0;
}