var info = {
 child : {consume : 1,range : [0,18]},
 adult : {consume : 2,range : [18,50]},
 old : {consume : 1.5,range : [50,200]},
};

function thirstyIn(water, ageOfDwellerArray) {
 var consumePerDay = 0;
 for(var i=0;i<ageOfDwellerArray.length;i++){
 for(var j in info){
 var type = info[j];
 var range = type.range;
 if(ageOfDwellerArray[i] >= range[0] && ageOfDwellerArray[i] < range[1]){
 consumePerDay += type.consume;
 break;
 }
 }
 }
 return consumePerDay ? Math.floor(water / consumePerDay) : -1;
}