Step program? Start, end, step integers - c++

Question

I've been stuck on this for almost two weeks now, could someone guide me? I'm supposed to have the user input an initial start value, and integer they want to end with, and a stepping integer (what the start value will be multiplied by).
EX.
Starting Integer: 10
Ending Integer: 200
Stepping Integer: 20
Output: 10, 30, 50, 70, 90, ...., 200
And when user inputs false values like a smaller ending integer than starting integer, message prompts them to try again.
I got the whole message prompting down I believe, not sure how to get the starting integer to be multiplied by stepping, and stop at ending integer.
This is the code I have so far:
#include <iostream>
#include <string>
using namespace std;
int main()
{
int step;
int stop;
int start = -1; //Local variable declaration
cout << "Please enter a positive integer you'd like to start with." << endl; //Starting integer
cin >> start;
if (start < 0)
cout << "Please enter a positive integer.";
if (start >= 0)
cout << "Please enter an integer to end with, it must be bigger than previous number chosen."; //Ending integer
cin >> stop;
if (stop < start)
cout << "Please enter a value that is larger than the previous number chosen." << endl;
if (stop > start)
cout << "Please enter the value you'd like to increase by." << endl; //Stepping integer
cin >> step;
cout << "Integers:";
while (start < stop)
{
cout << start << ", ";
start+=step;
}
return 0;
}
When I run it, it'll go through the entire for loop, and display the while loop but as only the stepping integer the user input, and then exits immediately.
EDIT - Code above is updated from previous code
Thanks for all the help so far! I've taken out the for loop as mentioned, and removed 'cin >> start;' after "Please enter a positive integer." - That was the reason why my program wasn't running through the whole cycle.
The program runs flawlessly if the user follows instructions first time around, however if they input a negative value first, they'll get the results below:
Input: -5
Output: Please put in a positive integer.
Input: 5
Output: Please enter the value you'd like to increase by.
And if they enter a stop value smaller than start value, they'll get the results below:
Input: 5
Output: Please enter a stop value larger....
Input: 3
Output: Integers:.........
How would I get the prompts to continue in order even after the user inputs negative value at first, and/or a smaller stop value than start? I don't think it'd be a cin; command, but please correct me if I'm wrong!

Answer 1

Maybe this can help:
int start = 10;
int stop = 200;
int step = 20;
do
{
cout << start << " ";
start = start + step; // increment. Shorter version: start += step;
} while (start < stop);
When getting the input try something like
int start = -1;
while(start < 0)
{
cout << "Please enter a positive integer you'd like to start with." << endl;
cin >> start;
}
and do something similar for stopand step, for instance
int end = -1;
while(end < start)
{
cout << "Please enter an integer to end with, it must be bigger than previous number chosen."; //Ending integer
cin >> end;
}

Answer 2

Instead of incrementing start by 1, increment it by step.
Also, you need to output the start variable, not step. Outputting step as you did before will just result in:
Integer: 20
Integer: 20
Integer: 20
....
Here are the changes I made:
cout << "Integers: ";
while(start < end)
{
cout << start << ", ";
start+=step;
}
Also, the for loop is not needed, it breaks out of it at the bottom regardless, so just delete the for loop.