Given an integer array, Find pairs of numbers which sum to a specified value

//OUTPUT : found elements 7 and 8
//         found elements 6 and 9

#include<iostream>
#include<set>

using namespace std;

int main(){
int a[] = {3,6,2,7,8,9,2,0,1,6};
int n = 15;
set<int> s;
int i;
set<int>::iterator it;
int len = sizeof(a)/sizeof(int);
for(i=0;i<len;i++){
it = s.find(n-a[i]);
if(it != s.end()){
cout<<"found elements "<<*it<<" and "<<a[i]<<endl;
} else {
s.insert(a[i]);
}
}
return 0;
}