d = int(input())
n = int(input())
przhm = list(map(int, input().split()))
slv = dict()
amn = 0
for i in range (len(przhm) - 1):
if przhm[i] == d:
continue
if przhm[i] not in slv:
slv[przhm[i]] = 1
else:
slv[przhm[i]] += 1
sps = slv.items()
for j in sps:
n_d = j[0] * j[1]
d_d = d * j[1]
amn = amn + (d_d - n_d)
print (amn)
#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;
}
34. Find First and Last Position of Element in Sorted Array | 33. Search in Rotated Sorted Array |
17. Letter Combinations of a Phone Number | 5. Longest Palindromic Substring |
3. Longest Substring Without Repeating Characters | 1312. Minimum Insertion Steps to Make a String Palindrome |
1092. Shortest Common Supersequence | 1044. Longest Duplicate Substring |
1032. Stream of Characters | 987. Vertical Order Traversal of a Binary Tree |
952. Largest Component Size by Common Factor | 212. Word Search II |
174. Dungeon Game | 127. Word Ladder |
123. Best Time to Buy and Sell Stock III | 85. Maximal Rectangle |
84. Largest Rectangle in Histogram | 60. Permutation Sequence |
42. Trapping Rain Water | 32. Longest Valid Parentheses |
Cutting a material | Bubble Sort |
Number of triangles | AND path in a binary tree |
Factorial equations | Removal of vertices |
Happy segments | Cyclic shifts |
Zoos | Build a graph |