C :

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

C++ :

#include <iostream>
#include <cstdio>
using namespace std;
int main()
{
    int n,max;
    cin>>max;
    cin>>n;
    if(n>max)
    {
        max=n;
    }
    cin>>n;
    if(n>max)
    {
        max=n;
    }
    cout<<max<<endl;
    return 0;
}

Pascal :

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