function checkInput() {
    var sfield = document.getElementById("sfield");
    var sfile = document.getElementById("sfile");
    
    if (sfile.value == "" && sfield.value == "") {
	var error = document.getElementById("error");
	error.style.display = "block";
	sfield.focus();
	return false;
    }
}

function addExample(){
    var field = document.getElementById("sfield");
    field.value = sequence;
    var file = document.getElementById("sfile");
    file.value = "";
    var matrix = document.getElementById("c");
    matrix.value = "pam250";
    var l = document.getElementById("l");
    l.value = 40;
}

var sequence = 
    ">SRC_RSVP\n"+
    "GLAKDAWEIPRESLRLEAKLGQGCFGEVWMGTWNDTTRVAIKTLKPGTMSPEAFLQEAQVMKKLRHEKLVQLYAV\n"+
    "VSEEPIYIVIEYMSKGSLLDFLKGEMGKYLRLPQLVDMAAQIASGMAYVERMNYVHRDLRAANILVGENLVCKVA\n"+
    "DFGLARLIEDNEYTARQGAKFPIKWTAPEAALYGRFTIKSDVWSFGILLTELTTKGRVPYPGMVNREVLDQVERG\n"+
    "YRMPCPPECPESLHDLMCQCWRKDPEERPTFKYLQAQLLPACVLEVAE\n\n"+
    ">YES_AVISY\n"+
    "GLAKDAWEIPRESLRLEVKLGQGCFGEVWMGTWNGTTKVAIKTLKLGTMMPEAFLQEAQIMKKLRHDKLVPLYAV\n"+
    "VSEEPIYIVTEFMTKGSLLDFLKEGEGKFLKLPQLVDMAAQIADGMAYIERMNYIHRDLRAANILVGDNLVCKIA\n"+
    "DFGLARLIEDNEYTARQGAKFPIKWTAPEAALYGRFTIKSDVWSFGILLTELVTKGRVPYPGMVNREVLEQVERG\n"+
    "YRMPCPQGCPESLHELMKLCWKKDPDERPTFEYIQSFLEDYFTAAEPSG\n\n"+     
    ">ABL_MLVAB\n"+
    "TIYGVSPNYDKWEMERTDITMKHKLGGGQYGEVYEGVWKKYSLTVAVKTLKEDTMEVEEFLKEAAVMKEIKHPNL\n"+
    "VQLLGVCTREPPFYIITEFMTYGNLLDYLRECNRQEVSAVVLLYMATQISSAMEYLEKKNFIHRDLAARNCLVGE\n"+
    "NHLVKVADFGLSRLMTGDTYTAHAGAKFPIKWTAPESLAYNKFSIKSDVWAFGVLLWEIATYGMSPYPGIDLSQV\n"+
    "YELLEKDYRMERPEGCPEKVYELMRACWQWNPSDRPSFAEIHQAFETMFQESSIS\n\n"+
    ">FES_FSVGA\n"+
    "VLNRAVPKDKWVLNHEDLVLGEQIGRGNFGEVFSGRLRADNTLVAVKSCRETLPPDIKAKFLQEAKILKQYSHPN\n"+
    "IVRLIGVCTQKQPIYIVMELVQGGDFLTFLRTEGARLRMKTLLQMVGDAAAGMEYLESKCCIHRDLAARNCLVTE\n"+
    "KNVLKISDFGMSREAADGIYAASGGLRQVPVKWTAPEALNYGRYSSESDVWSFGILLWETFSLGASPYPNLSNQQ\n"+
    "TREFVEKGGRLPCPELCPDAVFRLMEQCWAYEPGQRPSFSAIYQELQSIRKRHR\n\n"+
    ">FPS_FUJSV\n"+ 
    "VLTRAVLKDKWVLNHEDVLLGERIGRGNFGEVFSGRLRADNTPVAVKSCRETLPPELKAKFLQEARILKQCNHPN\n"+
    "IVRLIGVCTQKQPIYIVMELVQGGDFLSFLRSKGPRLKMKKLIKMMENAAAGMEYLESKHCIHRDLAARNCLVTE\n"+
    "KNTLKISDFGMSRQEEDGVYASTGGMKQIPVKWTAPEALNYGWYSSESDVWSFGILLWEAFSLGAVPYANLSNQQ\n"+
    "TREAIEQGVRLEPPEQCPEDVYRLMQRCWEYDPHRRPSFGAVHQDLIAIRKRHR\n\n"+ 
    ">KRAF_MSV36\n"+                                                 
    "SSYYWKMEASEVMLSTRIGSGSFGTVYKGKWHGDVAVKILKVVDPTPEQLQAFRNEVAVLRKTRHVNILLFMGYM\n"+
    "TKDNLAIVTQWCEGSSLYKHLHVQETKFQMFQLIDIARQTAQGMDYLHAKNIIHRDMKSNNIFLHEGLTVKIGDF\n"+
    "GLATVKSRWSGSQQVEQPTGSVLWMAPEVIRMQDDNPFSFQSDVYSYGIVLYELMAGELPYAHINNRDQIIFMVG\n"+
    "RGYASPDLSRLYKNCPKAIKRLVADCVKKVKEERPLFPQILSSIELLQHSLPKIN";