Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func configure(scanner *bufio.Scanner) {
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1000005), 1000005)
}
func getNextString(scanner *bufio.Scanner) string {
	scanned := scanner.Scan()
	if !scanned {
		panic("scan failed")
	}
	return scanner.Text()
}
func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}
func getNextInt64(scanner *bufio.Scanner) int64 {
	i, _ := strconv.ParseInt(getNextString(scanner), 10, 64)
	return i
}
func getNextFloat64(scanner *bufio.Scanner) float64 {
	i, _ := strconv.ParseFloat(getNextString(scanner), 64)
	return i
}
func main() {
	fp := os.Stdin
	wfp := os.Stdout
	extra := 0
	if os.Getenv("I") == "IronMan" {
		fp, _ = os.Open(os.Getenv("END_GAME"))
		extra = 100
	}
	scanner := bufio.NewScanner(fp)
	configure(scanner)
	writer := bufio.NewWriter(wfp)
	defer func() {
		r := recover()
		if r != nil {
			fmt.Fprintln(writer, r)
		}
		writer.Flush()
	}()
	solve(scanner, writer)
	for i := 0; i < extra; i++ {
		fmt.Fprintln(writer, "-----------------------------------")
		solve(scanner, writer)
	}
}
func solve(scanner *bufio.Scanner, writer *bufio.Writer) {
	a := getNextInt(scanner)
	b := getNextInt(scanner)
	c := getNextInt(scanner)
	if a == most(a, b, c) {
		fmt.Fprintln(writer, "A")
		return
	}
	if b == most(a, b, c) {
		fmt.Fprintln(writer, "B")
		return
	}
	fmt.Fprintln(writer, "C")
}

func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}
func most(a, b, c int) int {
	return max(a, max(b, c))
}

C++: //#define NDEBUG
#include <cstddef>
#include <cstdint>
#include <vector>

using i8 = ::std::int_least8_t;
using i32 = ::std::int_least32_t;
using i64 = ::std::int_least64_t;
using u8 = ::std::uint_least8_t;
using u32 = ::std::uint_least32_t;
using u64 = ::std::uint_least64_t;
using isize = ::std::ptrdiff_t;
using usize = ::std::size_t;

template <class T = usize> class rep {
	const T f, l;

public:
	class itr {
		friend rep;
		T i;
		constexpr itr(T x) noexcept : i(x) {}

	public:
		void operator++() noexcept { ++i; }
		constexpr T operator*() const noexcept { return i; }
		constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
	};
	constexpr rep(const T first, const T last) noexcept : f(first), l(last) {}
	constexpr itr begin() const noexcept { return itr(f); }
	constexpr itr end() const noexcept { return itr(l); }
};
template <class T = usize> class revrep {
	const T f, l;

public:
	class itr {
		friend revrep;
		T i;
		constexpr itr(T x) noexcept : i(x) {}

	public:
		void operator++() noexcept { --i; }
		constexpr T operator*() const noexcept { return i; }
		constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
	};
	constexpr revrep(const T first, const T last) noexcept : f(first), l(last) {}
	constexpr itr begin() const noexcept { return itr(l - 1); }
	constexpr itr end() const noexcept { return itr(f - 1); }
};
template <class T> bool amax(T &a, const T &b) {
	return a <= b ? (a = b, 1) : 0;
}
template <class T> bool amin(T &a, const T &b) {
	return b <= a ? (a = b, 1) : 0;
}
template <class T> bool asmax(T &a, const T &b) {
	return b <= a ? 0 : (a = b, 1);
}
template <class T> bool asmin(T &a, const T &b) {
	return a <= b ? 0 : (a = b, 1);
}
template <class T> using vec_alias = ::std::vector<T>;
template <class T> auto md_vec(usize n, const T &value) {
	return ::std::vector<T>(n, value);
}
template <class... Args> auto md_vec(usize n, Args... args) {
	return ::std::vector<decltype(md_vec(args...))>(n, md_vec(args...));
}
template <class T> const T &as_const(const T &v) noexcept { return v; }
template <class T> constexpr T difference(const T &a, const T &b) {
	return a <= b ? b - a : a - b;
}

#include <cassert>
#include <iterator>
#include <utility>

template <class Monoid, template <class> class Container> class segment_tree {
public:
	using value_structure = Monoid;
	using value_type = typename value_structure::value_type;
	using container_type = Container<value_type>;
	using const_reference = typename container_type::const_reference;
	using size_type = typename container_type::size_type;

protected:
	static size_type getsize(const size_type size) {
		size_type ret = 1;
		while (ret < size)
			ret <<= 1;
		return ret;
	}

	size_type size_;
	container_type tree;

	size_type base_size() const { return tree.size() >> 1; }
	void recalc(const size_type index) {
		tree[index] =
			value_structure::operation(tree[index << 1], tree[index << 1 | 1]);
	}

public:
	segment_tree() : size_(0), tree() {}
	explicit segment_tree(const size_type size)
		: size_(size), tree(getsize(size) << 1, value_structure::identity()) {}
	template <class InputIterator>
	segment_tree(InputIterator first, InputIterator last)
		: size_(::std::distance(first, last)), tree() {
		const size_type cap = getsize(size_);
		tree.reserve(cap << 1);
		tree.resize(cap, value_structure::identity());
		tree.insert(tree.end(), first, last);
		tree.resize(cap << 1, value_structure::identity());
		for (size_type i = cap - 1; i; --i)
			recalc(i);
	}

	bool empty() const { return !size_; }
	size_type size() const { return size_; }

	const_reference operator[](const size_type index) const {
		assert(index < size());
		return tree[index + base_size()];
	}
	value_type fold(size_type first, size_type last) const {
		assert(first <= last);
		assert(first <= size());
		assert(last <= size());
		value_type ret_l = value_structure::identity(),
			ret_r = value_structure::identity();
		for (first += base_size(), last += base_size(); first < last;
			first >>= 1, last >>= 1) {
			if (first & 1)
				ret_l = value_structure::operation(::std::move(ret_l), tree[first++]);
			if (last & 1)
				ret_r = value_structure::operation(tree[last - 1], ::std::move(ret_r));
		}
		return value_structure::operation(::std::move(ret_l), ::std::move(ret_r));
	}
	template <class F> size_type search(const F &f) const {
		if (f(value_structure::identity()))
			return 0;
		if (!f(tree[1]))
			return size() + 1;
		value_type acc = value_structure::identity();
		size_type i = 1;
		while (i < base_size())
			if (!f(value_structure::operation(acc, tree[i <<= 1])))
				acc = value_structure::operation(::std::move(acc), tree[i++]);
		return i - base_size() + 1;
	}

	template <class F> void update(size_type index, const F &f) {
		assert(index < size());
		index += base_size();
		tree[index] = f(::std::move(tree[index]));
		while (index >>= 1)
			recalc(index);
	}
};



#include <algorithm>
#include <iostream>
#include <utility>
#include <numeric>
#include <set>
#include<array>
#include<queue>

#include<string>

int main() {
	u32 a, b, c;
	std::cin >> a >> b >> c;
	if (a > b&&a > c) {
		std::cout << "A" << std::endl;
	}
	if (b > c&&b > a) {
		std::cout << "B" << std::endl;
	}
	if (c > a&&c > b) {
		std::cout << "C" << std::endl;
	}
	return 0;
}

C++: #include <iostream>
#include <set>
#include <vector>
#include <string>
#include <algorithm>
#include <iterator>
#include <map>
#include <utility>
#include <list>
#include <climits>
#include <bitset>
#include <numeric>

using namespace std;

#define rep(i, n) for(int i = 0; i < n; i++)
#define repi(i, n) for(auto i = (n).begin(); i != (n).end(); i++)
#define in_arr(type, a, n) copy_n(istream_iterator<type>(cin), n, (a).begin());
#define ll long long int

int main(){
    int a, b, c;
    cin >> a >> b >> c;
    if(a < c && b < c){
        cout << "C" << endl;
    }else if(a < b){
        cout << "B" << endl;
    }else{
        cout << "A" << endl;
    }
    return 0;
}

C++: #define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios::sync_with_stdio(false); cin.tie(0);
  int a, b, c;
  cin >> a >> b >> c;
  int mx = max({a, b, c});
  if (mx == a) cout << "A" << endl;
  if (mx == b) cout << "B" << endl;
  if (mx == c) cout << "C" << endl;
  return 0;	
}