in contests/abc223/abc223_c_another.rs [3:24]
fn main() {
input! {
n:usize,
abs:[(f64,f64);n],
}
let mut tot = 0.;
for &(a, b) in &abs {
tot += a / b;
}
let mut ans = 0.;
let mut cur = 0.;
for &(a, b) in &abs {
if cur + a / b > tot / 2. {
ans += (tot / 2. - cur) * b;
break;
} else {
ans += a;
cur += a / b;
}
}
println!("{}", ans);
}