{

void FindTwoSum(vector<int> &num, int id1, int id2, int target, vector<vector<int> > &ans)

{

int left=id2+1, right=num.size()-1;

while(left<right)

{

if(num[left]+num[right]<target)

left++;

else if(num[left]+num[right]>target)

right--;

else

{

vector<int> result;

result.push_back(num[id1]);

result.push_back(num[id2]);

result.push_back(num[left]);

result.push_back(num[right]);

ans.push_back(result);

int l=left+1, r=right-1;

while(l<num.size()&&num[l]==num[left])

l++;

left=l;

while(r>=0&&num[r]==num[right])

r--;

right=r;

}

}

}

vector<vector<int> > fourSum(vector<int> &num, int target)

{

vector<vector<int> > ans;

if(num.size()==0)

return ans;

sort(num.begin(), num.end());

int sum=0;

if(num[0]<0)

sum=-1*num[0];

for(int i=0;i<num.size();i++)

num[i]+=sum;

target+=4*sum;

int left1, right1, left2, right2;

left1=0;

while(left1<num.size())

{

left2=left1+1;

while(left2<num.size())

{

FindTwoSum(num, left1, left2, target-num[left1]-num[left2], ans);

right2=left2+1;

while(right2<num.size()&&num[right2]==num[left2])

right2++;

left2=right2;

}

right1=left1+1;

while(right1<num.size()&&num[right1]==num[left1])

right1++;

left1=right1;

}

for(int i=0;i<ans.size();i++)

{

for(int j=0;j<4;j++)

{

ans[i][j]-=sum;

}

}

return ans;

}