C :

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

C++ :

#include<iostream>
using namespace std;

int main(){
	int a,b,c,d,m;
	cin>>a>>b>>c>>d;
	//假设a最大
	m = a;
	//如果b比最大数m大
	if(b > m){
		m = b;
	}
	
	if(c > m){
		m = c;
	} 
	
	if(d > m){
		m = d;
	} 
	
	cout<<m<<endl;
}

Pascal :

var a:array[1..4] of longint;
    max,i:longint;
    begin
    max:=-maxlongint;
    for i:=1 to 4 do
    read(a[i]);
    for i:=1 to 4 do
    if a[i]>max then max:=a[i];
    write(max);
    end.

Java :

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int b = sc.nextInt();
		int c = sc.nextInt();
		int d = sc.nextInt();
		int max = 0 ;
		if(a>b&&a>c&&a>d) {
			max = a ;
		}
		if (b>a&&b>c&&b>d ) {
			max = b ;
		}
		if (c>a&&c>b&&c>d ) {
			max = c ;
		}
		if (d>a&&d>b&&d>c ) {
			max = d ;
		}
		System.out.println(max);
	}
}

Python :

a,b,c,d=map(int,input().split())
t=a
if t<a:
    t=a;
if t<b:
    t=b;
if t<c:
    t=c;
if t<d:
    t=d;
print(t)