var mailhost = "@yl.is.s.u-tokyo.ac.jp";
var username = location.pathname.match(/[o]{1}[s]{1}[u]{1}[m]{1}[i]{1}/);

//document.writeln(location);

//document.writeln('<a href=mailto:' + username + mailhost + '>' + username + mailhost + '</a>');
document.write(username + mailhost);