440B - Balancer - CodeForces Solution

#include <iostream>
#define int long long
using namespace std;

signed main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	int n, k = 0;
	cin >> n;
	int a[n], ans = 0;
	for (int &i : a) cin >> i, k += i;
	k /= n;
	for (int i = 1, m; i < n; i++) {
		m = k - a[i - 1];
		a[i - 1] += m, a[i] -= m;
		ans += abs(m);
	}
	cout << ans;
	return 0;
}