Go: package main

import "fmt"

func max(a, b int) int {
	if a < b {
		return b
	}
	return a
}

func max3(a, b, c int) int {
	return max(max(a, b), c)
}

func main() {
	var (
		a, b, c int
		ch      byte
	)
	fmt.Scanln(&a, &b, &c)
	m := max3(a, b, c)
	switch m {
	case a:
		ch = 'A'
	case b:
		ch = 'B'
	case c:
		ch = 'C'
	}
	fmt.Printf("%c\n", ch)
}

C++: #include<iostream>
using namespace std;
int main(){
    int a, b, c;
    cin >> a >> b >> c;
    if( a > b && a > c){
        cout << "A" << endl;
    }
    else if( b > a && b > c){
        cout << "B" << endl;
    }
    else if(c > a && c > b){
        cout << "C" << endl;
    }
    return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

typedef int _loop_int;
#define REP(i,n) for(_loop_int i=0;i<(_loop_int)(n);++i)
#define FOR(i,a,b) for(_loop_int i=(_loop_int)(a);i<(_loop_int)(b);++i)
#define FORR(i,a,b) for(_loop_int i=(_loop_int)(b)-1;i>=(_loop_int)(a);--i)

#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define DEBUG_VEC(v) cout<<#v<<":";REP(i,v.size())cout<<" "<<v[i];cout<<endl
#define ALL(a) (a).begin(),(a).end()

#define CHMIN(a,b) a=min((a),(b))
#define CHMAX(a,b) a=max((a),(b))

// mod
const ll MOD = 1000000007ll;
#define FIX(a) ((a)%MOD+MOD)%MOD

// floating
typedef double Real;
const Real EPS = 1e-11;
#define EQ0(x) (abs(x)<EPS)
#define EQ(a,b) (abs(a-b)<EPS)
typedef complex<Real> P;

int main(){
  int a,b,c;
  cin>>a>>b>>c;
  puts(a>b&&a>c ? "A" : (b>c ? "B" : "C"));
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define P pair<ll,ll>
#define FOR(I,A,B) for(ll I = ll(A); I < ll(B); ++I)
#define FORR(I,A,B) for(ll I = ll((B)-1); I >= ll(A); --I)
#define TO(x,t,f) ((x)?(t):(f))
#define SORT(x) (sort(x.begin(),x.end())) // 0 2 2 3 4 5 8 9
#define POSL(x,v) (lower_bound(x.begin(),x.end(),v)-x.begin()) //xi>=v  x is sorted
#define POSU(x,v) (upper_bound(x.begin(),x.end(),v)-x.begin()) //xi>v  x is sorted
#define NUM(x,v) (POSU(x,v)-POSL(x,v))  //x is sorted
#define REV(x) (reverse(x.begin(),x.end())) //reverse
ll gcd(ll a,ll b){if(a%b==0)return b;return gcd(b,a%b);}
ll lcm(ll a,ll b){ll c=gcd(a,b);return ((a/c)*(b/c)*c);}
#define NEXTP(x) next_permutation(x.begin(),x.end())
const ll INF=ll(1e18)+ll(7);
const ll MOD=1000000007LL;
#define out(a) cout<<fixed<<setprecision((a))
#define YesNo(a) cout<<((a)?"Yes":"No")<<endl;
#define YESNO(a) cout<<((a)?"YES":"NO")<<endl;

int main(){
	ll a,b,c,m;
	cin >> a >> b >> c;
	m = max({a,b,c});
	if(m==a){
		cout << "A" << endl;
	}else if(m==b){
		cout << "B" << endl;
	}else if(m==c){
		cout << "C" << endl;
	}
}

C++: #include <bits/stdc++.h>

using namespace std;

int main(){
  int a,b,c; cin >> a >> b >> c;
  int maxi=max({a,b,c});
  if(maxi==a) cout << 'A';
  else if(maxi==b) cout << 'B';
  else cout << 'C';
  cout << endl;
  
  return 0;
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <set>
#include <cmath>
#include <cstring>
#include <iomanip>
#include <random>
#include <chrono>
#include <queue>
using namespace std;
typedef long long ll;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;
#define INF 1000000000
#define MOD 1000000007
#define EPS 0.00000001

int main (){
    int mx = -INF;
    int idx = 0;
    for(int i=0; i<3; i++){
        int r; cin >> r;
        if(r>mx){
            mx = r;
            idx = i;
        }
    }
    
    string S = "ABC";
    cout << S[idx] << endl;
    return 0;
}