#include using namespace std; using ll = long long; using ld = long double; using pll = pair; using tlll = tuple; constexpr ll INF = 1LL << 60; template bool chmin(T& a, T b) {if (a > b) {a = b; return true;} return false;} template bool chmax(T& a, T b) {if (a < b) {a = b; return true;} return false;} ll safemod(ll A, ll M) {ll res = A % M; if (res < 0) res += M; return res;} ll divfloor(ll A, ll B) {if (B < 0) A = -A, B = -B; return (A - safemod(A, B)) / B;} ll divceil(ll A, ll B) {if (B < 0) A = -A, B = -B; return divfloor(A + B - 1, B);} ll pow_ll(ll A, ll B) {if (A == 0 || A == 1) {return A;} if (A == -1) {return B & 1 ? -1 : 1;} ll res = 1; for (int i = 0; i < B; i++) {res *= A;} return res;} ll mul_limited(ll A, ll B, ll M = INF) { return B == 0 ? 0 : A > M / B ? M : A * B; } ll pow_limited(ll A, ll B, ll M = INF) { if (A == 0 || A == 1) {return A;} ll res = 1; for (int i = 0; i < B; i++) {if (res > M / A) return M; res *= A;} return res;} ll logfloor(ll A, ll B) {assert(A >= 2); ll res = 0; for (ll tmp = 1; tmp <= B / A; tmp *= A) {res++;} return res;} ll logceil(ll A, ll B) {assert(A >= 2); ll res = 0; for (ll tmp = 1; tmp < B; tmp *= A) {res++;} return res;} ll arisum_ll(ll a, ll d, ll n) { return n * a + (n & 1 ? ((n - 1) >> 1) * n : (n >> 1) * (n - 1)) * d; } ll arisum2_ll(ll a, ll l, ll n) { return n & 1 ? ((a + l) >> 1) * n : (n >> 1) * (a + l); } ll arisum3_ll(ll a, ll l, ll d) { assert((l - a) % d == 0); return arisum2_ll(a, l, (l - a) / d + 1); } template void unique(vector &V) {V.erase(unique(V.begin(), V.end()), V.end());} template void sortunique(vector &V) {sort(V.begin(), V.end()); V.erase(unique(V.begin(), V.end()), V.end());} #define FINALANS(A) do {cout << (A) << '\n'; exit(0);} while (false) template void printvec(const vector &V) {int _n = V.size(); for (int i = 0; i < _n; i++) cout << V[i] << (i == _n - 1 ? "" : " ");cout << '\n';} template void printvect(const vector &V) {for (auto v : V) cout << v << '\n';} template void printvec2(const vector> &V) {for (auto &v : V) printvec(v);} //* #include using namespace atcoder; using mint = modint998244353; //using mint = modint1000000007; //using mint = modint; //*/ int main() { ll N; cin >> N; vector A(N); for (ll i = 0; i < N; i++) { cin >> A.at(i); } ll ans = 0; for (ll i = 0; i < N; i++) { ans += A.at(i) - (i == 0 ? 0 : A.at(i - 1)) - 1; } cout << ans << endl; }