#include <stdio.h>
using namespace std;

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

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);
        if (a > b && b != -1)
            nr += (a - b);
        b = a;
    }

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

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