#include <iostream>
#include <vector>
using namespace std;
int main() {
vector<int> ladder;
int size, sum = 0;
cin >> size;
ladder.resize(size);
for (int i = 0; i < size; ++i) {
cin >> ladder[i];
}
for (int i = 0; i < size; ++i) {
if (i + 1 < size && ladder[i] < 0) { // ladder[i] + ladder[i+1] < ladder[i + 1]
sum += ladder[i + 1];
++i;
}
else {
sum += ladder[i];
}
}
cout << sum;
}
