Sum of all numbers multiple of 3 or 5 less than 1000

#include<stdio.h>

int sum_multiple(int n,int range)
{
    int sum,num_of_terms=range/n;
    sum=n*num_of_terms*(num_of_terms+1)/2;
    return sum;
}

main()
{
    int ans=sum_multiple(3,1000);
    int ans1=sum_multiple(5,1000);
    int ans2=sum_multiple(15,1000);
    ans=ans+ans1-ans2;
    printf("%d",ans);
}