【bzoj3505】 Cqoi2014—数三角形

// bzoj3505
#include<algorithm>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<cmath>
#include<queue>
#define LL long long
#define inf 10000000
#define Pi acos(-1.0)
#define free(a) freopen(a".in","r",stdin),freopen(a".out","w",stdout);
using namespace std;

int n,m;
LL c[2000010][4];

int gcd(int a,int b) {
	return b==0 ? a : gcd(b,a%b);
}
int main() {
	scanf("%d%d",&n,&m);
	for (int i=0;i<=(n+1)*(m+1);i++) c[i][0]=1;
	for (int i=1;i<=(n+1)*(m+1);i++)
		for (int j=1;j<=min(3,i);j++) c[i][j]=c[i-1][j-1]+c[i-1][j];
	LL ans=c[(n+1)*(m+1)][3]-(n+1)*c[m+1][3]-(m+1)*c[n+1][3];
	for (int i=1;i<=n;i++)
		for (int j=1;j<=m;j++) {
			LL x=gcd(i,j)+1;
			if (x>2) ans-=(x-2)*2*(n-i+1)*(m-j+1);
		}
	printf("%lld",ans);
	return 0;
}