#include <stdio.h>
using namespace std;

int a, b = -1;
int n, i, nr;

int abs (int x)
{
    if (x < 0)
        return x * -1;
    return x;
}

int main ()
{
    FILE *f = fopen ("operatii.in","r");
    FILE *g = fopen ("operatii.out","w");
    fscanf (f,"%d", &n);
    for (i=1; i<=n; ++i)
    {
        fscanf (f,"%d", &a);
        nr += (abs (a - b));
        b = a;
    }
    nr += a;

    fprintf (g, "%d\n", nr / 2);

    fclose (g);
    fclose (f);
    return 0;
}