vector<string> split(string s, char ch)
{
vector<string> res;
int n = s.size();
int i = 0;
while(i < n)
{
int j = i + 1;
while(j < n && s[j] != ch) ++j;
res.push_back(s.substr(i, j - i));
i = j + 1;
}
return res;
}