#include <iostream>
#include <fstream>
using namespace std;
ifstream in("operatii.in");
ofstream out("operatii.out");
const int maxn = 1000005;
int v[maxn];
string str;
int n;
void citire()
{
    getline(in, str);
    getline(in, str);
    int sz = str.size();
    int poz = 0;
    int nr = 0;
    for(int i = 0; i < sz; i++)
    {
        if(str[i] >= '0' && str[i] <= '9')
            nr = nr * 10 + str[i] - '0';
        else
        {
            v[++poz] = nr;
            nr = 0;
        }
    }
    v[++poz] = nr;
}
int main()
{
    in >> n;
    citire();
    long long s = 0;
    for(int i = 1; i <= n; i++)
        if(v[i] - v[i-1] > 0)
            s = s + v[i] - v[i-1];
    out << s << "\n";
    return 0;
}