BZOJ2659: [Beijing wc2012]算不出的算式

转化成直线下点数

#include<cstdio>#include<iostream>#include<cstring>#include<cstdlib>#include<cmath>using namespace std;char c;#define ll long longinline void read(ll &a){   a=0;do c=getchar();while(c<'0'||c>'9');   while(c<='9'&&c>='0')a=(a<<3)+(a<<1)+c-'0',c=getchar();}int main(){    ll p,q;    read(p),read(q);    printf("%lld",(p^q)?((p-1)*(q-1)>>2):((p-1)*(p+1)>>2));    return 0;}