#include <iostream>
using namespace std;
const int N = 27;
 
int main() {
	// your code goes here
	long double f[N][N];
	for(int i=0; i<N; i++) {
		f[i][0] = f[0][i] = 1; // you will always win if you know one type of card has been depleted
	}
	for(int i=1; i<N; i++) {
		for(int j=1; j<N; j++) {
			f[i][j] = (abs(i-j) + i*f[i-1][j] + j*f[i][j-1])/(long double)(i+j);
		}
	}
	cout << "Your expected winnings are: " << f[N-1][N-1] << endl;
	return 0;
}

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