Scratch

im trying to do a simple project but im very new to scratch.  My project involves me creating a program where the user is prompted to enter a number, then they enter that many numbers (assuming the user is complying with the rules and will not enter a negative number) then, it will display the largest number, and then, if the user enters the number -1 the program finishes.  a few pointers in the right direction would really help me a lot.  thanks!