Ural 1091 Tmutarakan Exams

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long LL;
 4 const int maxn = 52;
 5 LL c[maxn][maxn];
 6 int p[] = {2,3,5,7,11,13,17,19,23,29};
 7 void init() {
 8     c[0][0] = 1;
 9     for(int i = 1; i < maxn; ++i) {
10         c[i][0] = c[i][i] = 1;
11         for(int j = 1; j < i; ++j)
12             c[i][j] = c[i-1][j] + c[i-1][j-1];
13     }
14 }
15 int main() {
16     init();
17     int k,s;
18     while(~scanf("%d%d",&k,&s)) {
19         LL ret = 0;
20         for(int i = 0; i < 10; ++i) {
21             if(s/p[i] < k) {
22                 for(int j = 1; j < (1<<i); ++j) {
23                     int cnt = 0;
24                     LL tmp = 1;
25                     for(int t = 0; t < i; ++t) {
26                         if((j>>t)&1) {
27                             cnt++;
28                             tmp *= p[t];
29                         }
30                     }
31                     if(cnt&1) ret += c[s/tmp][k];
32                     else ret -= c[s/tmp][k];
33                 }
34                 break;
35             }
36         }
37         printf("%I64d\n",ret > 10000?10000:ret);
38     }
39     return 0;
40 }