Why my code for 'The snail in the well' project in JavaScript course is wrong?

Question

function main() {
var depth = parseInt(readLine(), 10);
//your code goes here
var days = 0;
var feet = 0;
while(feet < depth){
feet = feet+7-2;
days++;
}
document.write(days);
}

Answer 1

oh. It's js code so use
console.log(days) ;
Instead of document.write(days);

Answer 2

Hint: if it reached on climbing 7 feet depth then it won't fall back 2 feet.

Answer 3

It still didn't work?
I put if statement,if after add 7 and feet it still lower than depth it will minus 2.
Is it because my code have error in it?

function main() {
var depth = parseInt(readLine(), 10);
//your code goes here
var days = 0;
var feet = 0;
while(feet < depth){
feet = feet + 7;
if(feet < depth){
feet = feet - 2;
}
days++;
}
document.write(days);
}