Working it out on paper will give you a better idea of how to do it. Your input is the number of days, you have a variable called days, so read the input into that variable. Having a variable called input is too vague. Does the number of days change? No. The day may change, but the number of days doesn't. Decide what each variable represents and name it accordingly.
for(int x = 0; x < input; x++)
{
days = cents;
total += days;
cents *= 2;
}
cout<<"\ntotal pay is :"<<total<<" cents";
Why would days be equal to cents?
Again, input is not a good name. Replace it with days, or better yet, numDays. cents is a better variable name than input, as is total, but I think you should use variable names like:
numDays
dailyPayInCents
totalPayInCents
One, it is much easier to follow, and two, I think using those variable names will make it much easier to figure out where everything goes.
Marked 
