#include <bits/stdc++.h>
#define rep(i, a, b) for (ll i = (ll)(a); i < (ll)(b); i++)
using namespace std;

typedef long long ll;

template <typename T, typename S> bool chmin(T &a, S b) {
    if (a > b) {
        a = b;
        return 1;
    }
    return 0;
}

int main() {
    int n;
    cin >> n;
    vector<int> a(n);
    rep(i, 0, n) cin >> a[i];
    n += 3;
    a.insert(a.begin(), 2e9);
    a.push_back(0);
    a.push_back(0);
    int nw = a[0];
    ll ans = 0;
    rep(i, 1, n - 1) {
        if (a[i - 1] < a[i] && a[i] > a[i + 1]) {
            ans += a[i] - nw;
            nw = a[i];
        }
        chmin(nw, a[i]);
    }
    cout << ans << endl;
}