#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int n,m,mat[100][100];
int check()
{
	int i,j;
	for(i=1;i<=n;i++)
		for(j=1;j<=m;j++)
			if(mat[i][j]!=1)
				return 0;
	return 1;
}
int main()
{
	freopen("minesweeper.in","r",stdin);
	freopen("minesweeper.out","w",stdout);
	int nrn,nrm,sec=0;
	scanf("%d%d",&n,&m);
	while(!check())
	{
		srand(time(NULL));
		nrn=rand()%n+1;
		srand(time(NULL));
		nrm=rand()%m+1;
		if(mat[nrn][nrm]==0)
			mat[nrn][nrm]=1;
		else
			mat[nrn][nrm]=0;
		sec++;
	}
	printf("%d\n",sec);
	return 0;
}