Submission #5236344

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Source Code Expand

#include <bits/stdc++.h>
#define REP(i, n) for(int i = 0;i < n;i++)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end())
#define VRSORT(v) sort(v.rbegin(), v.rend())
#define ll long long
#define pb(a) push_back(a)
#define MOD 1000000007
using namespace std;
typedef pair<int, int> P;
typedef pair<ll, ll> LP;
typedef pair<int, P> PP;
typedef pair<ll, LP> LPP;

typedef vector<unsigned int>vec;
typedef vector<vec> mat;
//typedef tuple<ll, ll, ll> T;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

void add(ll& a, ll b){a = (a+b) % MOD;}

int dy[]={0, 0, 1, -1, 0};
int dx[]={1, -1, 0, 0, 0};

double r,k,ans=0;
int n,m;

double calc(int x){
    if(x<=0 && x>=n) return 0;
    k=fabs(r-2*r/n*x);
    return sqrt(r*r-k*k)*2;
}
int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cin>>r>>n>>m;
    REP(i,n+m){
        ans+=max(calc(i),calc(i-m));
    }
    printf("%.8lf\n",ans);
}

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