#include<fstream>
using namespace std;
ifstream f("operatii.in");
ofstream g("operatii.out");
int n,m,i,mc,previouS,max1,ac,ap,rez;

int main()
{
    f>>n;
    f>>ap;
    mc=1;
    max1=ap;
    previouS=0;
    for(i=2;i<=n+1;i++)
    {
        ac=ap;
        f>>ap;
        if(mc==1)
        {
            if(ac<=ap) if(ap>max1) max1=ap;
                         else;
            else mc=0;
        }
        else if(mc==0)
        {
            if(ac<ap||i==n+1)
            {
                rez+=max1-previouS;
                max1=ap;
                previouS=ac;
                mc=1;
            }
        }
       // g<<ac<<" "<<ap<<" "<<rez<<" "<<max1<<"\n";
    }

    g<<rez+max1-previouS;

    return 0;
}