182B - Vasya's Calendar - CodeForces Solution

#include <bits/stdc++.h>

#define _freopen_in freopen("input.txt", "r", stdin)
#define _freopen_out freopen("output.txt", "w", stdout)
#define _fast_io ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define _cin_ignore cin.ignore(numeric_limits<streamsize>::max(), '\n')
#define _iterator(container) container.begin(), container.end()
#define _str(x) to_string((x))
#define _len(x) int(size((x)))
#define _max(x, y, z) max((x), max((y), (z)))
#define _min(x, y, z) min((x), min((y), (z)))
#define _print_list(list) for (auto x : list) { cout << x << " "; } cout << '\n'
#define _print_grid(grid) for (const auto& v : grid) { for (auto x : v) { cout << x << " "; } cout << '\n'; }
#define _print_map(mp) for (const auto& [ k, v ] : mp) { cout << k << ": " << v << endline; }
#define _lcm(x, y) (((x) * (y)) / __gcd((x), (y)))
#define _index_of(list, x) find(list.begin(), list.end(), (x)) - list.begin()
#define _sublist(list, x, y) decltype(list)(list.begin() + x, list.begin() + y + 1)
#define endline '\n'
#define MULTI_LINE(...) #__VA_ARGS__

constexpr long double PI = 3.14159265358979323846;
constexpr long long int MOD = (long long int)1e9 + 7;
constexpr long double eps = 5e-8;

using namespace std;

typedef long long int ll;
typedef unsigned long long int ull;

void run(int tc)
{
	int d, n;
	cin >> d >> n;

	int total = 0;
	vector<int> a(n);
	for (int i = 0; i < n; i++)
	{
		cin >> a[i];
	}

    for (int i = 0; i < n - 1; i++)
    {
        total += d - a[i];
    }

	cout << total << endline;
}

/**
 * Problem Name: 
 * Problem URL: 
 * References 1: 
 *
 * Solution Time Complexity: 
 * Solution Space Complexity: 
 *
 * @author zeus
 */
int main()
{
    _fast_io;
    // _freopen_in;

    int t = 1;
    // cin >> t;

    for (int i = 1; i <= t; i++)
    {
        // cout << "test case: " << i << endline;
        run(i);
    }

    return 0;
}