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