#include <bits/stdc++.h>
#define INF 2000000000000000000
#define ll long long
#define ld long double
#define pll pair<ll, ll>
using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  ll N, A, B;
  cin >> N >> A >> B;
  cout << N - A + B << "\n";
}

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

double dp[101][101][101];

double f(int x, int y, int z) {
    if (dp[x][y][z] > 0)  return dp[x][y][z];
    if (x == 100 || y == 100 || z == 100) return 0;

    double ret = 0;
    ret += x * (f(x + 1, y, z) + 1);
    ret += y * (f(x, y + 1, z) + 1);
    ret += z * (f(x, y, z + 1) + 1);
    ret /= x + y + z;
    return dp[x][y][z] = ret;
}

int main()
{
    int a, b, c;
    cin >> a >> b >> c;
    cout << setprecision(10) << f(a, b, c) << "\n"s;
    return 0;
}
