BZOJ2659: [Beijing wc2012]算不出的算式

式子转化成求(1,1)-((p-1)/2,(q-1)/2)矩阵中有多少个整数点…

#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>using namespace std;int read(){    char ch=getchar();int f=0,x=1;    while(ch<'0'||ch>'9'){if(ch=='-') x=-1;ch=getchar();}    while(ch>='0'&&ch<='9'){f=(f<<1)+(f<<3)+ch-'0';ch=getchar();}    return f*x;}int main(){    long long p,q;    cin>>p>>q;    if(p==q) cout<<(p*p-1LL)/4LL;    else cout<<(p-1LL)*(q-1LL)/4LL;}