Submission #4028617

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Source Code Expand

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

#define FOR(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define RFOR(i,a,b) for(int i=(int)(b)-1;i>=(int)(a);i--)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) RFOR(i,0,n)
#define LL long long
#define INF INT_MAX

const double EPS = 1e-14;
const double PI  = acos(-1.0);


int main(){
  double r, n, m;
  cin >> r >> n >> m;

  double d[int(1e6)] = {0};

  double x = n / 2;
  FOR (i, 1, n) {
    double length = 2 * sqrt((1 - pow((abs(x - i) / x), 2)) * pow(r, 2));
    d[int(m + i)] = length;
  }

  double ans = 0;
  REP (i, 1e6 - m) {
    ans += max(d[i], d[int(i + m)]);
  }
  printf("%.16lf\n", ans);
}

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