C++ :

#include<bits/stdc++.h>
using namespace std;
long long a[10];
int main()
{
	cin>>a[1]>>a[2]>>a[3];
    sort(a+1,a+4);
    if(a[1]+a[2]>a[3]&&a[1]+a[3]>a[2]&&a[2]+a[3]>a[1])
    {
    	if(a[3]*a[3]==a[1]*a[1]+a[2]*a[2])
    	    cout<<"Yes！";
    	else
    	    cout<<"No！";
    }
    else
        cout<<"Error！";
	
	return 0;
}

Pascal :

var
  a,b,c:longint;
begin
  readln(a,b,c);
  if (a+b>c)and(a+c>b)and(b+c>a) then
    if (a*a+b*b=c*c)or(a*a+c*c=b*b)or(b*b+c*c=a*a) then
      writeln('Yes！')
      else writeln('No！')
    else writeln('Error！');
end.