#include <iostream>
#include <vector>
using namespace std;
typedef long long ll;
const int maxn = 50005;
struct node_data {
    int sum, prefix, suffix, res;
};

node_data merge_nodes(node_data A, node_data B) {
    node_data C;

    C.sum = A.sum + B.sum;
    C.prefix = max(A.prefix, A.sum + B.prefix);
    C.suffix = max(B.suffix, B.sum + A.suffix);

    C.res = max(max(A.res, B.res), A.suffix + B.prefix);

    return C;
}

node_data make_node(int value) {
    node_data C;
    C.sum = value;
    C.prefix = max(0, value);
    C.suffix = max(0, value);
    C.res = max(0, value);

    return C;
}
int main() {
    ios_base::sync_with_stdio(false);

    node_data A = make_node(2);
    node_data B = make_node(-3);
    node_data C = make_node(4);

    A = merge_nodes(A, B);
    C = merge_nodes(A, C);

    cout << C.res << endl;
    return 0;
}