C :

#include <stdio.h>

void main(){
	int a,b,c,t;
	double s;
	scanf("%d%d%d",&a,&b,&c);
	
	if(a > b){
		t=a;a=b;b=t;
	}
	
	if(b > c){
		t=b;b=c;c=t;
	}
	
	if(a*a+b*b==c*c){
		s = a * b / 2.0;
		printf("%.1f",s); 
	}else{
		printf("No"); 
	}
}

C++ :

#include<iostream>
#include <iomanip>
using namespace std;
int main(){
	int a,b,c,t;
	double s;//面积
	cin>>a>>b>>c;
	if(a>b){
		t=a;
		a=b;
		b=t;
		
	}
	if(b>c){
		t=b;
		b=c;
		c=t;
	}

	
	if(a*a+b*b==c*c){
		s = a * b * 1.0 / 2;
		cout<<fixed<<setprecision(1)<<s<<endl;
		
	}else{
		cout<<"No"<<endl;
	}
}

Pascal :

var a:array[1..5] of longint;
    i,j,t:longint;
    s:real;
begin
  for i:=1 to 3 do
   read(a[i]);
  for i:=1 to 2 do
   for j:=i+1 to 3 do
    if a[i]>a[j] then begin t:=a[i];a[i]:=a[j];a[j]:=t; end;
  if a[1]*a[1]+a[2]*a[2]=a[3]*a[3] then
    begin s:=a[1]*a[2]/2; writeln(s:0:1); end
   else writeln('No');
end.

Java :

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scanner=new Scanner(System.in);
		String str=scanner.nextLine();
		String[] strarray=str.split(" ");
		double a=Double.valueOf(strarray[0]);
		double b=Double.valueOf(strarray[1]);
		double c=Double.valueOf(strarray[2]);
		Double s=0.0;
		String result;
		if((a+b>c)&&(b+c>a)&&(a+c>b)){
			if(a*a==b*b+c*c){
				s=(double)(b*c)/2;
			}else if(b*b==a*a+c*c){
				s=(double)(a*c)/2;
			}else if(c*c==a*a+b*b){
				s=(double)(a*b)/2;
			}else{
			}
		}else{
		}
		if(s!=0.0){
			 result = String.format("%.1f",s);
		}else{
			 result="No";
		}
		System.out.println(result);		
	}
}

Python :

a,b,c=map(int,input().split(" "))
if a**2+b**2==c**2:
    s=0.5*a*b
    print("%.1f"%s)
elif a**2+c**2==b**2:
    s=0.5*a*c
    print("%.1f"%s)
elif b**2+c**2==a**2:
    s=0.5*b*c
    print("%.1f"%s)
else:
    print("No")