#!/usr/bin/bash
NUMOUT=${1}

NUMFILES=`ls input* | wc -l`

((IN_PER_OUT=${NUMFILES} / ${NUMOUT} + 1))

CURRENT=1
OUT=1
ls input* | while read FILE
do
  if [ ${CURRENT} -eq 1 ]
  then
    cat ${FILE} > output_${OUT}.txt
  else
    cat ${FILE} >> output_${OUT}.txt
  fi

  ((CURRENT=${CURRENT}+1))
  if [ ${CURRENT} -gt ${IN_PER_OUT} ]
  then
    CURRENT=1
    ((OUT=${OUT}+1))
  fi
done