#include<fstream>
using namespace std; 
ifstream f("dreptunghiuri.in");
ofstream g("dreptunghiuri.out");
int main() 
{int n,m,i,j,nr=0,q;
long long s=0;
	f>>n>>m;
for(i=1;i<=n-1;i++) 
{for(j=1;j<=m-1;j++) 
	nr++;}
for(q=1;q<=nr;q++) 
	s+=q; 
g<<s;
}