Not looping but grabs 40 rather than 20 instagram items

google spreadsheet instagram grabber

function addTitles() {
    var sheet = SpreadsheetApp.getActiveSheet();
    // sets up the header row for the sheet
    sheet.appendRow(['User Name', 'Likes Count', 'Comment Count', 'URL', 'Caption', 'Filter', 'Created Time']);
}



// attempt to loop to get next_url

    var search = 'dog'; // search term
    var client_id = 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX';
    var url = 'https://api.instagram.com/v1/tags/' + search + '/media/recent?client_id=' + client_id; // replace this with your API client ID
   
      
        function getInstagramData(searchTerm) {
        var result = UrlFetchApp.fetch(url);
        var json = JSON.parse(result.getContentText());
        var grams = json.data;
        var next_url = json.pagination.next_url
        var resultb = UrlFetchApp.fetch(next_url);
        var jsonb = JSON.parse(resultb.getContentText());
        var gramsb = jsonb.data;
        
//Logger.log(result);
//Logger.log(next_url);

        // Instagram gives you 20 on the first request
                for (var i = 0; i <= 20; i++) {
                    logGram_(grams[i]);
                    logGram_(gramsb[i]);
        }
          
              
        }

          
  function logGram_(gram) {
            var log = [];
            // pushes the various elements into the spreadsheet 
            log.push(gram.user.username);
            log.push(gram.likes.count);
            log.push(gram.comments.count);
            log.push(gram.link);
            log.push(gram.caption.text);
            log.push(gram.filter);
            log.push(gram.created_time);

            SpreadsheetApp.getActiveSheet().appendRow(log)
  }