#include <iostream>
#include <cmath>
#include <algorithm>
#include <string>
#include <vector>
#include <map>
#include <unordered_map>
#include <queue>
#include <set>
#include <unordered_set>
#include <complex>
#include <list>
#include <chrono>
#include <random>
#include <stack>
#include <iomanip>
#include <fstream>
using namespace std;
#define endl "\n"
// #define int long long
const int INF = 2 * 1e5 + 5;
const int MOD = 1e9 + 7;
void solve(){
int n;
cin >> n;
vector<int> a(n);
for(int i = 0; i < n; i++){
cin >> a[i];
}
int l = 1, r = n-2, sol = a[l];
while(l < r){
if(a[l] <= a[r]){
while(a[l] <= a[r] && l < r){
// cout << "1: " << l << " " << r << "| " << sol << endl;
sol += abs(a[l+1] - a[l]);
l++;
}
} else {
while(a[r] <= a[l] && l < r){
// cout << "2: " << l << " " << r << "| " << sol << endl;
r--;
}
}
}
cout << sol << endl;
}
int32_t main(){
ios_base::sync_with_stdio(false); cin.tie(nullptr);
int t = 1;
// cin >> t;
while(t--) solve();
return 0;
}
