Language: C++

// solutions.cpp : This file contains the 'main' function. Program execution
// begins and ends there.
//
// Run program: Ctrl + F5 or Debug > Start Without Debugging menu
// Debug program: F5 or Debug > Start Debugging menu

// Tips for Getting Started:
//   1. Use the Solution Explorer window to add/manage files
//   2. Use the Team Explorer window to connect to source control
//   3. Use the Output window to see build output and other messages
//   4. Use the Error List window to view errors
//   5. Go to Project > Add New Item to create new code files, or Project > Add
//   Existing Item to add existing code files to the project
//   6. In the future, to open this project again, go to File > Open > Project
//   and select the .sln file
#include <algorithm>
#include <array>
#include <bitset>
#include <climits>
#include <cmath>
#include <complex>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> coord;
typedef vector<int> veci;
typedef vector<coord> coords;
typedef vector<coords> adjuw;
typedef vector<veci> adjuu;
const int mod = 1000000007;
const int mod2 = 998244353;

#define mp make_pair
#define pb push_back

#define wl(a) while (a--)
#define FORCINNM(lim, arr)                                                     \
  for (int i = 0; i < lim; ++i) {                                              \
    cin >> arr[i];                                                             \
  }
#define FORCINPB(lim, arr)                                                     \
  for (int i = 0, t; i < lim; ++i) {                                           \
    cin >> t;                                                                  \
    arr.push_back(t);                                                          \
  }

bitset<1001> visiteddfs, visitedbfs;

void dfs(adjuu& graph, int vertex) {
	cout << vertex << ' ';
	visiteddfs[vertex] = true;
	for (int child : graph[vertex]) {
		if (!visiteddfs[child]) {
			dfs(graph, child);
		}
	}
}

void bfs(adjuu& graph, int vertex) {
	visitedbfs[vertex] = true;
	queue<int> vertices;
	vertices.push(vertex);
	while (!vertices.empty()) {
		int v = vertices.front();
		cout << v << ' ';
		vertices.pop();
		for (int child : graph[v]) {
			if (!visitedbfs[child]) {
				visitedbfs[child] = true;
				vertices.push(child);
			}
		}
	}
}

bool isprime(ull n) {
	if (n % 2 == 0) {
		return n == 2;
	}
	if (n % 3 == 0) {
		return n == 3;
	}
	ull k = sqrt(n);
	for (int i = 5; i <= k; i += 2) {
		if (n % k == 0) {
			return false;
		}
	}
	return n != 1;
}

void addedge(adjuw& adj, int v1, int v2, int wt) {
	adj[v1].emplace_back(v2, wt);
	adj[v2].emplace_back(v1, wt);
}

void addedge(adjuu& adj, int v1, int v2) {
	adj[v1].push_back(v2);
	adj[v2].push_back(v1);
}

int main() {
	ios_base::sync_with_stdio(false); cin.tie(0);
	int k; string s;
	cin >> k >> s;
	if (s.size > k) cout << s.substr(k) + "...";
	else cout << s;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:120:15: error: invalid use of member function 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size() const [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; size_type = long unsigned int]' (did you forget the '()' ?)
  120 |         if (s.size > k) cout << s.substr(k) + "...";
      |             ~~^~~~
      |                   ()