typedef tree<pair<int,int>, null_type, less<pair<int,int>>, rb_tree_tag,
tree_order_statistics_node_update>
PBDS;
int main(){
PBDS st;
//{value,index}
st.insert({1,0});
st.insert({10,1});
st.insert({15,2});
st.insert({9,3});
st.insert({07,4});
st.insert({1,5});
cout << st.order_of_key({5,6}) << endl; // line 1
cout << st.order_of_key({7,4}) << endl;// line 2
Why am i getting an error in line 2 and how to get desired result?
