#include <fstream>

using namespace std;

ifstream in("operatii.in");
ofstream out("operatii.out");

long long nr,nr1,N,op;

inline long long modul(long long a){ if(a<0)return -a; else return a;}

int main()
{
    in>>N;
    while(N--)
    {
        in>>nr1;
        op+= modul(nr1-nr);
        nr=nr1;
    }
    op+=nr;
    out<<op/2;
    return 0;
}