1 /************************************************************** 2     Problem: 2348 3     User: rausen 4     Language: C++ 5     Result: Accepted 6     Time:128 ms 7     Memory:1196 kb 8 ****************************************************************/ 9  10 #include <cstdio>11 #include <algorithm>12  13 using namespace std;14 typedef long long ll;15 typedef double lf;16 const int N = 100005;17 const lf eps = 1e-8;18  19 int n, a[N];20 ll ans;21  22 inline int read() {23     int x = 0, sgn = 1;24     char ch = getchar();25     while (ch < ‘0‘ || ‘9‘ < ch) {26         if (ch == ‘-‘) sgn = -1;27         ch = getchar();28     }29     while (‘0‘ <= ch && ch <= ‘9‘) {30         x = x * 10 + ch - ‘0‘;31         ch = getchar();32     }33     return sgn * x;34 }35  36 int main() {37     int i, j;38     n = read();39     for (i = 1; i <= n; ++i)40         a[i] = read();41     sort(a + 1, a + n + 1);42     for (i = j = 1; i <= n; ++i) {43         while (a[j] + eps < (lf) a[i] * 0.9)44             ++j;45         ans += i - j;46     }47     printf("%lld\n", ans);48     return 0;49 }