// Concert

function calcul()
{ a = document.concert.adulte.value * 10 ;
  b = document.concert.enfant.value * 5 ; 
  c = a + b ;
  
  document.concert.ttl_ad.value = a ;
  document.concert.ttl_en.value = b ; 
  document.concert.ttl.value = c + "€"}