妈呀这个世界的数论实在是太可怕了。。。
Orz iwtwiioi(给完传送门赶紧跑)
1 /************************************************************** 2 Problem: 2820 3 User: rausen 4 Language: C++ 5 Result: Accepted 6 Time:3508 ms 7 Memory:127760 kb 8 ****************************************************************/ 9 10 #include <cstdio> 11 #include <algorithm> 12 13 using namespace std; 14 typedef long long ll; 15 const int N = 1e7 + 5; 16 17 int n, m; 18 int p[N], u[N], g[N], cnt; 19 bool vis[N]; 20 21 inline int read() { 22 int x = 0; 23 char ch = getchar(); 24 while (ch < '0' || '9' < ch) 25 ch = getchar(); 26 while ('0' <= ch && ch <= '9') { 27 x = x * 10 + ch - '0'; 28 ch = getchar(); 29 } 30 return x; 31 } 32 33 void get_g() { 34 int i, j, k; 35 u[1] = 1; 36 for (i = 2; i < N; ++i) { 37 if (!vis[i]) 38 p[++cnt] = i, u[i] = -1, g[i] = 1; 39 for (j = 1; j <= cnt; ++j) { 40 if ((k = i * p[j]) >= N) break; 41 vis[k] = 1; 42 if (i % p[j] == 0) { 43 u[k] = 0, g[k] = u[i]; 44 break; 45 } 46 u[k] = -u[i], g[k] = u[i] - g[i]; 47 } 48 } 49 for (i = 1; i < N; ++i) 50 g[i] += g[i - 1]; 51 } 52 53 ll work(int n, int m) { 54 ll res = 0; 55 int i, j; 56 for (i = 1; i <= n; i = j + 1) { 57 j = min(n / (n / i), m / (m / i)); 58 res += 1ll * (g[j] - g[i - 1]) * (n / i) * (m / i); 59 } 60 return res; 61 } 62 63 int main() { 64 int T; 65 T = read(); 66 get_g(); 67 while (T--) { 68 n = read(), m = read(); 69 if (n > m) swap(n, m); 70 printf("%lld\n", work(n, m)); 71 } 72 return 0; 73 }