#include #include using namespace std;typedef long long LL;const LL N = 1e6 + 10;LL n;LL a[N]; LL ans = 0;int main(){ios::sync_with_stdio(false);cin.tie(0), cout.tie(0);cin >> n;for (int i = 1; i <= n; ++i){cin >> a[i];}if (n == 1)cout << a[1] << ".0000000000" << endl;else if (n == 2)cout << abs(a[2] - a[1]) << ".0000000000" << endl;else{LL temp = abs(a[n] - a[n - 1]);for (int i = n - 2; i >= 1; --i){ans = abs(a[i] - temp);temp = ans;}cout << ans << ".0000000000" << endl;}return 0;}