http://www.cplusplus.com/reference/algorithm/upper_bound/
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Return iterator to lower bound

Returns an iterator pointing to the first element in the range [first,last) which does not compare less than val.

Return iterator to upper bound

Returns an iterator pointing to the first element in the range [first,last) which compares greater than val.

 // lower_bound/upper_bound example

 #include <iostream>     // std::cout

 #include <algorithm>    // std::lower_bound, std::upper_bound, std::sort

 #include <vector>       // std::vector

 int main () {

   int myints[] = {,,,,,,,};

   std::vector<int> v(myints,myints+);           // 10 20 30 30 20 10 10 20

   std::sort (v.begin(), v.end());                // 10 10 10 20 20 20 30 30

   std::vector<int>::iterator low,up;

   low=std::lower_bound (v.begin(), v.end(), ); //          ^

   up= std::upper_bound (v.begin(), v.end(), ); //                   ^

   std::cout << "lower_bound at position " << (low- v.begin()) << '\n';

   std::cout << "upper_bound at position " << (up - v.begin()) << '\n';

   return ;

 }