1 #include <cstdio>
 2 #include <iostream>
 3 using namespace std;
 4 const int INF = 0x3f3f3f3f;
 5 int w[1005], v[1005], sum[1005];
 6 double dp[1005];
 7 int main()
 8 {
 9     int b, l, n;
10     while (cin >> b >> l >> n, b || l || n)
11     {
12         for (int i = 1; i <= n; i++) dp[i] = INF;
13         for (int i = 1; i <= n; i++)
14         {
15             cin >> w[i] >> v[i];
16             sum[i] = sum[i - 1] + w[i];
17         }
18         dp[1] = (double)l / v[1];
19         for (int i = 2; i <= n; i++)
20         {
21             int minn = v[i];
22             for (int j = i; j >= 1; j--)
23             {
24                 if (sum[i] - sum[j - 1] > b) continue;
25                 minn = min(minn, v[j]);
26                 dp[i] = min(dp[i], dp[j - 1] + (double)l / minn);
27             }
28         }
29         printf("%.1f\n", dp[n] * 60);
30     }
31     return 0;
32 }