#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++) {
    int in;
    cin >> in;
    a[i] = in;
    if (in < 0) in *= -1;
    sum += in;
  }
  cout << sum << endl;
}
