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