#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  vector<int> vec(n);
  int sum = 0;
  for (auto i = 0; i < (long long)(n); i++) {
    cin >> vec[i];
    sum += (abs(vec[i]));
  }
  cout << sum << '\n';
  return 0;
}
