#include <bits/stdc++.h>
#define rep(i, a) for (int i = (int)0; i < (int)a; ++i)
#define rrep(i, a) for (int i = (int)a - 1; i >= 0; --i)
#define REP(i, a, b) for (int i = (int)a; i < (int)b; ++i)
#define RREP(i, a, b) for (int i = (int)a - 1; i >= b; --i)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
using ll = long long;
constexpr ll mod = 1e9 + 7;
constexpr ll INF = 1LL << 60;

template <class T>
inline bool chmin(T &a, T b)
{
	if (a > b)
	{
		a = b;
		return true;
	}
	return false;
}
template <class T>
inline bool chmax(T &a, T b)
{
	if (a < b)
	{
		a = b;
		return true;
	}
	return false;
}

ll gcd(ll n, ll m)
{
	ll tmp;
	while (m != 0)
	{
		tmp = n % m;
		n = m;
		m = tmp;
	}
	return n;
}

ll lcm(ll n, ll m)
{
	return abs(n) / gcd(n, m) * abs(m); //gl=xy
}

using namespace std;

void solve()
{
	int n;
	cin>>n;
	vector<ll>y(n);
	rep(i,n)cin>>y[i];
	ll ans=0;
	REP(i,1,n-1){
		if(y[i-1]<y[i]){
			if(y[i]>y[i+1]){
				ll v=max(y[i-1],y[i+1]);
				ans+=y[i]-v;
				y[i]=v;
			}
		}
	else if(y[i-1]>y[i]){
			if(y[i]<y[i+1]){
				ll v=min(y[i-1],y[i+1]);
				ans+=-y[i]+v;
				y[i]=v;
			}
		}
	}
	if(n-3>=0){
		if(y[n-3]>y[n-2]){
			ans+=y[n-3]-y[n-2];
			y[n-2]=y[n-3];
		}
	}
	if(n-2>=0){
		if(y[n-2]>y[n-1]){
			ans+=y[n-2]-y[n-1];
			y[n-1]=y[n-2];
		}
	}
	//rep(i,n)cout<<y[i]<<endl;
	cout<<ans<<endl;
}

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout << fixed << setprecision(15);
	solve();
	return 0;
}