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