my %data;
while (<>) {
    chomp;
    my ($k, $v) = split /\t/;
    $data{$k}[0]++
    $data{$k}[1]+= $v;
}

local $, = "\t";
local $\ = "\n";
for my $k (keys %data) {
    my $data = $data{$k};
    print $k, $data->[0], $data->[1]/$data->[0];
}