Write a program in c++ to find the Sum of GP series

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

 float g1,cr,i,n,j;
    int ntrm,gpn;
    float sum=0;

     cout<<"Find the Sum of GP series.:\n ";
    cout<<"Input the first number of the G.P. series: ";
    cin>>g1;
    cout<<"Input the number or terms in the G.P. series: ";
    cin>>ntrm;
    cout<<"Input the common ratio of G.P. series: ";
    cin>>cr;
/*-------- generate G.P. series ---------------*/
     cout<<"\nThe numbers for the G.P. series:\n ";
     cout<<"1  ";
     for(j=1;j<=ntrm;j++)
       {
        gpn=pow(cr,j);
        cout<<"  "<<gpn;
       }
/*-------- End of G.P. series generate ---------------*/
    sum = (g1*(1 - (pow(cr,ntrm+1))))/(1-cr);
       n = g1 * (pow(cr,ntrm-1));
    cout<<"\nThe tn terms of G.P. : "<<n;
    cout<<"\nThe Sum of the G.P. series : "<<sum<<endl;
         system ("pause");
}

Test Data :
Input the first number of the G.P. series: 1
Input the number or terms in the G.P. series: 5
Input the common ratio of G.P. series: 2
Expected Output :
The numbers for the G.P. series:
1 2 4 8 16 32
The n terms of G.P. : 16.000000

The Sum of the G.P. series : 63.000000