Runtime error on test 5

#include<bits/stdc++.h>
#define ll long long
const ll M=1000000007;
using namespace std;

int main() {
	ll n,k,ans=0;
	cin>>k>>n;
	ans=(n%M)*(k%M)%M;
	for(ll i=1,a=0;i<=min(n,k);i=a+1){
		a=min(k%M/(ll)(k%M/i%M)%M,n%M)%M;
		ans=(ans-(((a%M+i%M)%M*(k%M/i%M)%M)%M*(a%M-i%M+1)%M)%M*500000004ll%M)%M;
	}
	cout<<(ans+M)%M;
    return 0;
}