Write a c++ program to find out the sum of in A.P. series. .

#include <iostream>
using namespace std;
void main()
{

    int n1,df,n2,i,ln;
    int s1=0;

         cout<<" Find out the sum of A.P. series :\n ";
   
         cout<<"Input  the starting number of the A.P. series: ";
         cin>>n1;
         cout<<"Input the number of items for  the A.P. series: ";
         cin>>n2;
         cout<<"Input  the common difference of A.P. series: ";
        cin>>df;
        s1 = ( n2 * ( 2 * n1 + ( n2 -1 ) * df ) )/ 2;
        ln = n1 + (n2-1) * df;
        cout<<"\nThe Sum of the  A.P. series are : \n";
        for(i=n1;i<=ln; i= i + df )
   {
             if (i != ln)
                cout<<" + "<<i;
             else
                cout<<i<<"  =  "<<s1<<endl;
         }
         system ("pause");
}



Test Data :
Input the starting number of the A.P. series: 1
Input the number of items for the A.P. series: 10
Input the common difference of A.P. series: 4
Expected Output :
The Sum of the A.P. series are :
1 + 5 + 9 + 13 + 17 + 21 + 25 + 29 + 33 + 37 = 190