C :

#include<stdio.h>
int main()
{
	int a,b,c,n;
	scanf("%d%d%d",&a,&b,&c);
	if(a<b)
	{
		n=a;
		a=b;
		b=n;
	}
	if(a<c)
	{
		n=c;
		c=a;
		a=n;
	}
	printf("%d\n",a);
}

C++ :

#include<stdio.h>
int main()
{
	int a,b,c;
	scanf("%d %d %d",&a,&b,&c);
	if(a<b)
	{
		a=b;
	}
	if(a<c)
	{
		a=c;
	}
	printf("%d\n",a);
	return 0;
}

Pascal :

var
   a,b,c,max:longint;
begin
 readln(a,b,c);
 max:=a;
 if b>max then max:=b;
 if c>max then max:=c;
 writeln(max);
end.