#include using namespace std; using ll = long long; int main() { ios::sync_with_stdio(false); cin.tie(0); int n; cin >> n; pair prv, cur; array dp{}; for(int i = 0; i < n; i++){ array ndp{}; auto [pa, pb] = prv; auto &&[a, b] = cur; cin >> a >> b; for(int j = 0; j < 2; j++){ for(int k = 0; k < 2; k++){ ndp[k] = max(ndp[k], dp[j] + (pb == a ? a : 0) + (a == b ? a : 0)); swap(a, b); } swap(pa, pb); } prv = cur; dp = ndp; } cout << max(dp[0], dp[1]) << '\n'; }