#include <bits/stdc++.h>

class Int {
public:
  long x;
  Int() { scanf("%ld", &x); }
  operator long() { return x; }
};

void get(int& x) { scanf("%d", &x); }

template<typename T> T add(const T& x, const T& y) { return x + y; }

template<typename T>
class Array {
public:
  T* p; int size; int seek;
  Array(int N) { p = new T[N]; size = N; seek = 0; for(int i = 0; i < N; ++i) get(p[i]); }
  Array(int N, T x) { p = new T[N]; for(int i = 0; i < N; ++i) p[i] = x; size = N; seek = 0; }
  const T& operator() (int i) const { return p[i]; }
};
template<typename T> inline Array<T> update(Array<T>& xs, int i, const T& x) { Array<T> res = xs; res.p[i] = x; xs.p = nullptr; return res; }
template<typename T, typename U> inline T foldl1(Array<T>& xs, U f) { T res = xs(0); for(int i = 1; i < xs.size; ++i) { res = f(res, xs(i)); } return res; }

int main() {
  Int N;
  Array<int> A(N);
  Int v;
  int res = foldl1(A, add<int>) - v;
  printf("%d\n", res);
  
  return 0;
}