# include <fstream>
# define DIM 1000010
using namespace std;
ifstream fin("operatii.in");
ofstream fout("operatii.out");
int v[DIM],n,i,dif;
long long s;
int main () {
    fin>>n;
    for(i=1;i<=n;i++){
        fin>>v[i];
        if(v[i]-dif>=0){
            s+=v[i]-dif;
            dif=v[i];
        }
        else
            dif=v[i];
    }
    fout<<s<<"\n";
    return 0;
}