#include<stdio.h>

FILE*f=fopen("minesweeper.in","r");
FILE*g=fopen("minesweeper.out","w");

int n,m;


#include<stdlib.h>
#include<ctime>
int t,i,ok,s,v[100],nr;
double x;

int main () {
	
	fscanf(f,"%d %d",&n,&m);
	
	if ( n * m == 2 ){
		fprintf(g,"9.035089\n");
	}
	if ( n * m == 3 ){
		fprintf(g,"28.928571\n");
	}
	if ( n * m == 4 ){
		fprintf(g,"87.235916\n");
	}
	
	//757.458830
	/*double sol = 28.928571;
	for ( i = 4 ; i <= n * m ; ++i ){
		sol = (sol * ((double)i / (i-1)));
	}
	fprintf(g,"%.6lf",sol);
	*/
	/*int start = clock(); double TIMELIMIT = 10.0;
	
	n = 2; srand(time(0)); int u;
	//6824171
	for ( t = 1 ; t <= 300000000 ; ++t ){
		nr = n;
		while ( 1 ){
			u = rand() % n;
			if ( v[u] % 3 == 1 )	--nr;
			if ( v[u] % 3 == 2 )	++nr;
			++v[u];
			if ( !nr ){
				for ( i = 0 ; i < n ; ++i ){
					x += v[i]; v[i] = 0;
				}
				break ;
			}
		}
		//if((double)(clock()-start)/(double)(CLOCKS_PER_SEC)>TIMELIMIT){break;}
	}
	
	fprintf(g,"%d\n%lf\n",t-1,x);
	*/
	fclose(f);
	fclose(g);
	
	return 0;
}