Please check my code....i am getting WA for few test cases

#include<bits stdc++.h="">

using namespace std;

int n,k;

vector<int> a;

int dp[1000002][2];

int f(int pos, int dir){

if(pos>=n || pos<0)

return -1000000006;

if(pos==0)

return a[pos];

if(dp[pos][dir] !=-1000000006)

return dp[pos][dir];