var checkedNb = false;
			var checkedInc = false;

			function display( )
			{
				if( checkedNb && checkedInc )
				{
					var nb = parseInt( document.getElementById( "nbpers" ).value );
					var inc = document.getElementById( "revenu" ).value;
					var mono = document.getElementById( "mono" ).checked;
					var sco = document.getElementById( "sco" );

					nb = (mono) ? 0.5 + nb : nb;

					if( (inc / nb) <= 8000 )
						sco.innerHTML = "3990 &euro;/an (-30%)";
					else
						sco.innerHTML = "5700 &euro;/an";
				}
				else
					alert( "Champs de saisie invalides" );
			}
			
			function check( input )
			{
				if( isInteger(input.value) )
				{
					input.style.color = "#000000";
					if( input.id == "nbpers" )
						checkedNb = true;
					else
						checkedInc = true;
				}
				else
				{
					input.style.color = "#FF0000";
					if( input.id == "nbpers" )
						checkedNb = false;
					else
						checkedInc = false;
				}
			}

			function isInteger( s )
			{
				return ( s.toString().search(/^[0-9]+$/) == 0 );

			}