function checkmsg(){
form = document.forms['smsgate'];
str = form.message.value;
msglength= str.length;

smslimit_first = 160;
smslimit_second = 146;
smslimit_firstsecond = 306;
smslimit_base = 153;
smslimit_last = 82;
smslimit_max = 760;
smslimit_strip = 760;

smscount = 0;

if(msglength <= smslimit_first){
  smscount = 1;
  smsin = 0;
  smslimit = smslimit_first;
}
else{
  if(msglength > smslimit_first && msglength <= smslimit_firstsecond){
    smscount = 2;
    smsin = smslimit_first;
    smslimit = smslimit_second;
  }
  else{
    if(msglength > smslimit_firstsecond){
      smscount = (2+(Math.ceil((msglength-smslimit_firstsecond)/smslimit_base)));
      smsin = (smslimit_firstsecond+((smscount-3)*smslimit_base));
      smslimit = smslimit_base;
    }
  }
}


document.getElementById('smscount').innerHTML=smscount;
document.getElementById('writelimitsms').innerHTML=(smslimit-(msglength-smsin));

if(msglength > smslimit_max){
    form.message.value=str.substring(0,smslimit_strip);
    alert('Do jedné zprávy nemužete napsat více než ' + smslimit_max + ' znaků. Další text odešlete v jiné zprávě.');
}

}

function checkgw(){

form = document.forms['smsgate'];
gateway = form.gateway;

var idgw = 0;
for(i=0;i<gateway.length;i++){
  if(gateway[i].checked==true){
    idgw = gateway[i].value;
    break;
  }
}

return idgw;
}

function showgw(){

var idgw = checkgw();

  if(idgw == 1){
    document.getElementById('option4').style.backgroundColor='#ffffff';
    document.getElementById('option1').style.backgroundColor='#efefef';
    document.getElementById('gatewayinfo4').style.display = 'none';
    document.getElementById('gatewayinfo1').style.display = 'block';
  }else{
    document.getElementById('option1').style.backgroundColor='#ffffff';
    document.getElementById('option4').style.backgroundColor='#efefef';
    document.getElementById('gatewayinfo1').style.display = 'none';
    document.getElementById('gatewayinfo4').style.display = 'block';
  }  
  
}