read
sort -nk3,3 -nk1,1|awk 'lc==$3{if($1-lt<0.5){lt=$2}else{print ls-0.5,lt,lc;ls=$1;lt=$2}}lc!=$3{print ls-0.5,lt,lc;ls=$1;lt=$2}{lc=$3}END{print ls-0.5,lt,lc}'|sed 1d|awk '{print $1,"s";print $2,"t"}'|sort -nk1,1|awk '$2=="s"{c++;m=(c>m)?c:m}$2=="t"{c--}END{print m}'