#include<stdio.h>
struct Rectangle {
    float length;
    float width;
};
float calculateArea(struct rectangle r){
    return r.length * r.width;
}
int main(){
    struct Rectangle rect;
    scanf("%f", &rect.length);
    scanf("%f", &rect.width);
    
    if (rect.length < 0 || rect.width <0){
        printf("Invalid Input");
    }else {
        float area = calculate(rect);
        printf("%.2f", area);
    }
    return 0;
}