IOI '94 P1 - The Triangle

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    int n; cin >> n;
    vector<int> mx(1);
    for (int i = 1; i <= n; ++i) {
        vector<int> mx2(n);
        for (int j = 0; j < i; ++j) {
            int x; cin >> x;
            if (j) mx2[j] = max(mx2[j], mx[j-1]);
            if (j!=i-1) mx2[j] = max(mx2[j], mx[j]);
            mx2[j] += x;
        }
        mx = mx2;
    }
    cout << *max_element(mx.begin(), mx.end()) << endl;
    return 0;
}