#include<stdio.h>
int main()
{
    float length,width,area;
    scanf("%f",&length);
    scanf("%f",&width);
    if(length<0||width||<0||length>100||width)
    {
        printf("Invalid input");
        return 0;
    }
    area=length*width;
    printf("2f",area);
    return 0;
}