text: class Solution {
  public:
      int maxWidthOfVerticalArea(vector<vector<int>>& ar) {
          int n = ar.size();
          set<int> s;
          for( int i = 0 ; i < n ; i++ )
              s.insert(ar[i][0]);
          set<int>::iterator it1,it2;
          it1 = s.begin();
          it2 = it1;
          it2++;
          int ans = 0;
          while(it2 != s.end()) {
              ans = max(ans,(*it2)-(*it1));
              it1++;
              it2++;
          }
          return ans;
      }
  };