#include using namespace std; typedef pair P; typedef pair> PP; typedef long long ll; const double EPS = 1e-8; const int INF = 1e9; const int MOD = 1e9+7; int dy[] = {0,1,0,-1}; int dx[] = {1,0,-1,0}; int main(void) { int n; cin >> n; int sum = 0; for(int i=0;i