3. Addition of N natural number divisible by 3 and 5 by C and CPP program

#include <iostream>
using namespace std;
void sumo(int a){
    int sum = 0;
    for(int i=1; i<a; i++)
    {
        if(i%3==0 || i%5==0)      //checking the condition of divisiblity
        {         
            sum+=i;               //adding the divisible condition satisfied number
        }
    }
    cout<<sum;
}
int main(){ 
    int n;
    cin>>n;
    int arr[n];               //declaration of the array for taking n number of the array
    for(int i = 0;i<n;i++)        //taking the n number if the input
    {
      cin>>arr[i];
    }
    for(int b=0; b<n; b++)        //using loop calling the function for every value 
    {
        sumo(arr[b]);             //printing the value out by the function
           cout<<"\n";
    }
    return 0;
}

/* for c user instead of using (10)cout<<sum; you will use printf("%d",sum); and on the place of   (17)cin>>a[i] you'll use 
scanf("%d",&arr[i]);