#include<stdio.h>
#include<math.h>
#include<vector>
using namespace std;
#define E 0.0000000001

int main( void )
{
	FILE *in = fopen( "maximum.in", "r" );
	while( 1 ){
		int m, p, a, b;
		fscanf( in, "%d%d%d%d", &m, &p, &a, &b );
		if( feof( in ) )
			break;
		double ra = sqrt( a );
		double ira = 1.0 / ra;
		double r = 0;
		for( int i = 0; i < m; i ++ ){
			double xm = b * ra - ra * i + (m-1-i) * ira;
			if( xm > ra + E || xm < -ira - E )
				continue;
			double score =
				pow( ra, p ) * i +
				pow( ira, p ) * (m-1-i) +
				pow( xm, p );
			r = max( r, score );
		}
		printf( "%.3lf\n", r );
	}
	fclose( in );
	return 0;
}