#include <cstdio>
#include <iostream>
#include <bitset>

using namespace std;
int v[1000001],w[1000010];
char f [100001];
int main()
{
    FILE *fin=fopen ("operatii.in","r");
    FILE *fout=fopen ("operatii.out","w");
    int n,m,i,mini,baz;
    long long sol=0;
    fscanf (fin,"%d",&n);
    m=1;
    w[m]=0;
    mini=0;
    for (i=1;i<=n;i++){
        fscanf (fin,"%d",&v[i]);
        if (v[i]!=v[i-1])
            w[++m]=v[i];
    }
    w[++m]=0;
    baz=0;
    for (i=2;i<m;i++){
        if (w[i]>w[i-1] && w[i]>w[i+1])
            sol+=w[i]-baz;
        if (w[i-1]>w[i] && w[i]<w[i+1])
            baz=w[i];
    }
    fprintf (fout,"%lld",sol);
    return 0;
}