#include <bits/stdc++.h>   using namespace std;   template <typename T, typename U>   inline void smin(T &a, U b) {     if (a > b) a = b;   }   template <typename T, typename U>   inline void smax(T &a, U b) {     if (a < b) a = b;   }   template <class T>   inline void gn(T &first) {     char c, sg = 0;     while (c = getchar(), (c >  9  || c <  0 ) && c !=  - )       ;     for ((c ==  -  ? sg = 1, c = getchar() : 0), first = 0; c >=  0  && c <=  9 ;          c = getchar())       first = (first << 1) + (first << 3) + c -  0 ;     if (sg) first = -first;   }   template <class T, class T1>   inline void gn(T &first, T1 &second) {     gn(first);     gn(second);   }   template <class T, class T1, class T2>   inline void gn(T &first, T1 &second, T2 &z) {     gn(first);     gn(second);     gn(z);   }   template <class T>   inline void print(T first) {     if (first < 0) {       putchar( - );       return print(-first);     }     if (first < 10) {       putchar( 0  + first);       return;     }     print(first / 10);     putchar(first % 10 +  0 );   }   template <class T>   inline void printsp(T first) {     print(first);     putchar(   );   }   template <class T>   inline void println(T first) {     print(first);     putchar(  n );   }   template <class T, class U>   inline void print(T first, U second) {     printsp(first);     println(second);   }   template <class T, class U, class V>   inline void print(T first, U second, V z) {     printsp(first);     printsp(second);     println(z);   }   int power(int a, int b, int m, int ans = 1) {     for (; b; b >>= 1, a = 1LL * a * a % m)       if (b & 1) ans = 1LL * ans * a % m;     return ans;   }   int ch[300010], re[300010], a[300010];   int C(int n, int m) {     return ((long long)ch[n] * re[m] % 1000000007) * (long long)re[n - m] %            1000000007;   }   void pre() {     ch[0] = 1;     for (int i = 1; i < 300010; i++)       ch[i] = (long long)ch[i - 1] * i % 1000000007;     re[300010 - 1] = power(ch[300010 - 1], 1000000007 - 2, 1000000007);     for (int i = 300010 - 1; i > 0; i--)       re[i - 1] = (long long)re[i] * i % 1000000007;     return;   }   int main() {     pre();     int n;     gn(n);     for (int i = 1; i <= n; i++) gn(a[i]);     if (n == 1) {       printf( %d n , a[1]);       return 0;     }     if (n == 2) {       printf( %d n , ((a[1] + a[2]) % 1000000007 + 1000000007) % 1000000007);       return 0;     }     if (n & 1) {       for (int i = 1; i < n; i++) {         if (i & 1)           a[i] = ((a[i] + a[i + 1]) % 1000000007 + 1000000007) % 1000000007;         else           a[i] = ((a[i] - a[i + 1]) % 1000000007 + 1000000007) % 1000000007;       }       n--;     }     if (n == 2) {       printf( %d n , (a[1] + a[2]) % 1000000007);       return 0;     }     long long ans1 = 0, ans2 = 0;     int m = n / 2;     for (int i = 1; i <= n; i++) {       if (i & 1) {         ans1 =             (ans1 + (long long)C(m - 1, i / 2) * a[i] % 1000000007) % 1000000007;       } else {         ans2 = (ans2 + (long long)C(m - 1, i / 2 - 1) * a[i] % 1000000007) %                1000000007;       }     }     if (m & 1 == 1)       printf( %I64d n , (ans1 + ans2) % 1000000007);     else       printf( %I64d n , ((ans1 - ans2) % 1000000007 + 1000000007) % 1000000007);     return 0;   }