How would i make a pascal triangle that keeps adding another star until it hits the end limit

so I have 3 inputs a,b,c

ex 4, 7, 1

++++
+++++
++++++
+++++++

its supposed to look like this, it starts at 4 stars and keeps adding another star c times until it reaches 7
how would I code this Im very confused this is what I have so far

#include <iostream>
#include <iomanip>

int main(){
    int r,a,b,c;
    std::cin>> a;
    std::cin>>b;
    std::cin>>c;
    for(int i = a; i <= b; i++) {
        for(int j = 1; j <=i; j++){
            std::cout << "*";
        }
        std::cout << "\n" ;
    }

}
    

>Solution :

While a is smaller than b, print "*" a times, then increment by c (step) for next iteration.

int main(){
    int a,b,c;
    std::cin>> a;
    std::cin>>b;
    std::cin>>c;
 while(a < b){
    for (int i =0; i < a;i++){
        cout << "*";
    }
    cout << endl;
    a+=c;
    }
    return 0;
}