#include <iostream>
#include <fstream>
#define LL long long
using namespace std;

LL N,res;

int main(){
    ifstream fin("operatii.in");
    ofstream fout("opeartii.out");
    fin >> N;

    int i,last,cr;
    for (i=1; i<=N; i++){
        fin >> cr;
        if (i!=1)
            if (cr<last) res+=(last-cr);

        last=cr;
    }

    res+=cr;
    fout << res << "\n";

    return 0;
}