Drupal 8 twig template creating issue in sum of content.field_output

Question

I am doing some customization in my views-view-table.html.twig file i would like to add content.field_output values

My code is

{% set f_v = content.field_output * 1 %}
{{ f_v }}

Or

{% set f_v = content.field_output + 1 %}
{{ f_v }}

Both code are not working