#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int ans = 0;
  for (int i = 0; i < n; i++) {
    int val;
    cin >> val;
    if (val >= 0)
      ans += val;
    else
      ans -= val;
  }
  cout << ans << endl;
}
