模积和(bzoj 2956)

#include <bits/stdc++.h>
 
using namespace std;
const int mod=19940417;
const int ni=3323403;
typedef long long ll;
 
ll sum(ll l,ll r)
{
    return (r-l+1)*(l+r)/2%mod;
}
ll cal(ll n)
{
    ll l,r,ans=n*n%mod;
    l=1;
    while(l<=n)
    {
        r=n/(n/l);
        ans=(ans-(n/l)*sum(l,r)%mod+mod)%mod;
        l=r+1;
    }
    return ans;
}
 
ll pre(ll l,ll r)
{
    return (r*(r+1)%mod*(2*r+1)%mod*ni%mod-l*(l+1)%mod*(2*l+1)%mod*ni%mod+mod)%mod;
}
 
int main()
{
    ll m,n;
    scanf("%lld%lld",&m,&n);
    if(m<n) swap(m,n);
    ll ans=(cal(n)*cal(m)%mod-n*n%mod*m%mod+mod)%mod;
    ll l=1,r;
    while(l<=n)
    {
        ll x,y;
        r=min(n/(n/l),m/(m/l));
        x=n/l;y=m/l;
        ans=(ans+sum(l,r)*(n*y%mod+m*x%mod)%mod-x*y%mod*pre(l-1,r)%mod+mod)%mod;
        l=r+1;
    }
    printf("%lld\n",ans);
    return 0;
}