Submission #61814693

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Source Code Expand

#include<bits/stdc++.h>
using namespace std; 
using i64 = long long;

void solve() {
    i64 R; cin >> R;
    auto ok = [&](i64 x, i64 h) -> bool {
        return (2 * x + 1) * (2 * x + 1) + (2 * h + 1) * (2 * h + 1) <= 4 * R * R;
    };
    i64 ans = 0;
    for (i64 x = 0; x < R; x++) {
        i64 low = 0, high = R + 1;
        while (low + 1 < high) {
            i64 m = (low + high) >> 1;
            if (ok(x, m)) {
                low = m;
            } else {
                high = m;
            }
        }
        if (x == 0) {
            ans += 4 * low + 1;
        }else {
            ans += 4 * low;
        }
    }
    cout << ans << '\n';
} 

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int tt = 1;
    // cin >> tt;
    for(int t = 1; t <= tt; t++) {
        solve();
    }
}

Submission Info

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