#include <stdio.h>


double mul(double x, double y);

int main (void){
	double x;
	double y;
	double ans;
	double (*pm)(double x, double y);
	pm=mul;
	ans=(*pm)(x,y);
	printf("ans=%lf\n",ans);
	return 0;
}

double mul(double x, double y){
	return x*y;
}