#include using namespace std; using ll = long long; using pii = pair; using pll = pair; using vi = vector; using vl = vector; #define rep3(i, a, b, c) for (ll i = (a); i < (b); i += (c)) #define rep2(i, a, b) rep3(i, a, b, 1) #define rep1(i, n) rep2(i, 0, n) #define rep0(n) rep1(aaaaa, n) #define ov4(a, b, c, d, name, ...) name #define rep(...) ov4(__VA_ARGS__, rep3, rep2, rep1, rep0)(__VA_ARGS__) #define per(i, a, b) for (ll i = (a) - 1; i >= (b); i--) #define fore(e, v) for (auto&& e : v) #define all(a) begin(a), end(a) #define sz(a) (int)(size(a)) #define lb(v, x) (lower_bound(all(v), x) - begin(v)) #define eb emplace_back template bool chmin(T& a, const S& b) { return a > b ? a = b, 1 : 0; } template bool chmax(T& a, const S& b) { return a < b ? a = b, 1 : 0; } const int INF = 1e9 + 100; const ll INFL = 3e18 + 100; #define i128 __int128_t struct _ { _() { cin.tie(0)->sync_with_stdio(0), cout.tie(0); } } __; int main(){ int N; cin>>N; stack>T; int ans=0; T.push({(int)2e9,1}); rep(i,N){ int H; cin>>H; while(T.top()[0]<=H){ auto [h,c]=T.top(); T.pop(); if(c==0)ans-=h; else ans+=h; } if(T.top()[1]!=i%2){ if(i%2)ans-=H; else ans+=H; T.push({H,i%2}); } cout<