#include <fstream>
using namespace std;
ifstream fin("operatii.in");
ofstream fout("operatii.out");

long long motorization(int n, long long last, int now, long long sum) {
    long long x;
    fin >> x;
    ++now;
    if (last < x) {
        sum += x - last;
        last = x;
        if (now != n)
            return motorization(n, last, now, sum);
    }
    if (now == n)
        return sum;
    last = x;
    return motorization(n, last, now, sum);
}

int main()
{
    int n;
    fin >> n;
    fout << motorization(n, 0, 0, 0);
    return 0;
}