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OI-codes/Luogu/P3743/P3743.cpp

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2021-01-03 06:30:50 +00:00
#include <bits/stdc++.h>
using namespace std;
int n;
double p, a[100005], b[100005];
double sum, l, r = 1e10, mid;
bool check(double mid) {
double q = mid * p;
sum = 0;
for (int i = 0; i < n; i++) {
if (a[i] * mid > b[i]) {
sum += a[i] * mid - b[i];
}
}
return sum <= q;
}
int main() {
cin >> n >> p;
for (int i = 0; i < n; i++) {
cin >> a[i] >> b[i];
sum += a[i];
}
if (sum <= p) {
cout << -1 << endl;
return 0;
}
while (r - l > 1e-6) {
mid = (l + r) / 2;
if (check(mid)) {
l = mid;
} else {
r = mid;
}
}
cout << fixed << setprecision(10) << l << endl;
return 0;
}