luoguP4132 [BJOI2012]算不出的等式 数论

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 #include<queue>
 5 #define ms(a,b) memset(a,b,sizeof a)
 6 #define rep(i,a,n) for(int i = a;i <= n;i++)
 7 #define per(i,n,a) for(int i = n;i >= a;i--)
 8 #define inf 1000000007
 9 using namespace std;
10 typedef long long ll;
11 typedef double D;
12 #define eps 1e-8
13 ll read() {
14     ll as = 0,fu = 1;
15     char c = getchar();
16     while(c < ‘0‘ || c > ‘9‘) {
17         if(c == ‘-‘) fu = -1;
18         c = getchar();
19     }
20     while(c >= ‘0‘ && c <= ‘9‘) {
21         as = as * 10 + c - ‘0‘;
22         c = getchar();
23     }
24     return as * fu;
25 }
26 //head
27 ll p,q,ans;
28 int main() {
29     p = read(),q = read();
30     ans = (p>>1)*(q>>1);
31     if(p == q) ans += p>>1;
32     printf("%lld\n",ans);
33     return 0;
34 }