Submission #7042097

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Source Code Expand

#include<iostream>
#include <iomanip>
#include<algorithm>
#include<cmath>
using namespace std;

double calcb(long long r,long long n, long long k){
    long double p = (float)r/n;
    // 2倍にして返していることに注意。
    // さらに2倍
    float ans;
    if (n*k < 0) {
        cout << "error:" << n << " " << k << endl;
    }
    ans = sqrt(k*(n-k)) * p; // (r/n);
    return 4 * ans;
}

int main() {
    cout << setprecision(20); //
    long long r,n,m;
    long double g=0;
    cin >> r >> n >> m;
    for (int i=1;i<=n+m-1;i++) {
        if (i<=m) {g += calcb(r,n,i);}
        else if (i <= n-1) {g += max(calcb(r,n,i),calcb(r,n,i-m));}
        else {g += calcb(r,n,i-m);}
    }
    cout << g << endl;
    return 0;
}

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