How to take data backup using cassandra-snapshotter?

I have to take the data backup of my cassandra nodes and upload it to amazon AWS s3. When I execute the following command,

cassandra-snapshotter --aws-access-key-id=**** --aws-secret-access-key=**** --s3-bucket-name=inblox-exp-buck --s3-bucket-region=ap-southeast-2 --s3-base-path=test1 backup --hosts=52.64.45.152,52.64.28.145 --user=ubuntu

I get the following error,

[52.64.45.152] Executing task 'node_start_backup'
[52.64.28.145] Executing task 'node_start_backup'

Fatal error: Needed to prompt for a connection or sudo password (host: 52.64.28.145), but input would be ambiguous in parallel mode

Aborting.
Needed to prompt for a connection or sudo password (host: 52.64.28.145), but input would be ambiguous in parallel mode

Fatal error: Needed to prompt for a connection or sudo password (host: 52.64.45.152), but input would be ambiguous in parallel mode

Aborting.
Needed to prompt for a connection or sudo password (host: 52.64.45.152), but input would be ambiguous in parallel mode

Fatal error: One or more hosts failed while executing task 'node_start_backup'

Aborting.
[52.64.45.152] Executing task 'clear_node_snapshot'
[52.64.28.145] Executing task 'clear_node_snapshot'
[52.64.28.145] sudo: /usr/bin/nodetool clearsnapshot -t "20150416144918"
[52.64.45.152] sudo: /usr/bin/nodetool clearsnapshot -t "20150416144918"

Fatal error: Needed to prompt for a connection or sudo password (host: 52.64.28.145), but input would be ambiguous in parallel mode

Aborting.
Needed to prompt for a connection or sudo password (host: 52.64.28.145), but input would be ambiguous in parallel mode

Fatal error: Needed to prompt for a connection or sudo password (host: 52.64.45.152), but input would be ambiguous in parallel mode

Aborting.
Needed to prompt for a connection or sudo password (host: 52.64.45.152), but input would be ambiguous in parallel mode

Fatal error: One or more hosts failed while executing task 'clear_node_snapshot'

Aborting.
One or more hosts failed while executing task 'clear_node_snapshot'

What is happening here? How do I fix this problem ?