#include <bits/stdc++.h>
using namespace std;
#define int long long

int N;
int INF = 1e18;

signed main(){
  cin>>N;
  vector<int> A(N);
  for(int i = 0; i < N; i++) cin>>A[i];
  vector<vector<int>> dp(N+1,vector<int>(2,-INF));
  dp[1][1] = -A[0];
  for(int i = 1; i < N; i++){
  	dp[i+1][1] = max({dp[i][1],dp[i][0]+A[i]*-1,A[i]*-1});
  	dp[i+1][0] = max(dp[i][0],dp[i][1]+A[i]);
  }
  int ans = -INF;
  for(int i = 0; i <= N; i++) ans = max(ans,max(dp[i][0],dp[i][1]));
  cout << ans << "\n";
}