/**
 * File  : 643_Operatii.cpp
 * Author: Cristian Dinu (Dr.Optix)
 * URL   : http://infoarena.ro/problema/operatii
 */

#include <stdio.h>

long long int a[1000010],i,n,k;

int main ()
{
    freopen("operatii.in","r",stdin);
    freopen("operatii.out","w",stdout);

    scanf("%lld",&n);
    for(int i=0;i<n;i++)
    {
        scanf("%lld",&a[i]);
    }
    k=a[0];
    for (i=0;i<n-1;i++)
    {
        if (a[i+1]>a[i])
        {
            k=k+(a[i+1]-a[i]);
        }
    }
    printf ("%lld",k);

    return 0;
}