finding fibonacci numbers

Hi, guys, I'm having problems with this short program. The version without functions is below and it does not work properly. I might be making a logical mistake somewhere...
This program asks user for n, and displays its Fibonacci number calculated iteratively. Then the program continues calculating Fibonaccis and stops when it reaches a Fib that would not fit in a 100-cell array (one cell per digit). It is supposed to display the largest Fib that still fits in the array.
I would appreciate if you could look at it with a "fresh" eye...
Thanks