#ifdef NACHIA
#define _GLIBCXX_DEBUG
#else
#define NDEBUG
#endif
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using i64 = long long;
using u64 = unsigned long long;
#define rep(i,n) for(i64 i=0; i<i64(n); i++)
const i64 INF = 1001001001001001001;
template<typename A> void chmin(A& l, const A& r){ if(r < l) l = r; }
template<typename A> void chmax(A& l, const A& r){ if(l < r) l = r; }
using namespace std;


void testcase(){
    i64 N; cin >> N;
    vector<i64> A(N); rep(i,N) cin >> A[i];
    i64 ans = max<i64>(A.back(), 0) - min<i64>(A.front(), 0);
    ans *= 2;
    cout << ans << "\n";
}

int main(){
    ios::sync_with_stdio(false); cin.tie(nullptr);
    rep(f,1) testcase();
    return 0;
}