Problem p02550 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#include <iostream>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define speed                                                                  \
  ios_base::sync_with_stdio(0);                                                \
  cin.tie(0);                                                                  \
  cout.tie(0);
#define ll long long
#define pb push_back
#define mem1(a) memset(a, -1, sizeof(a))
#define mem0(a) memset(a, 0, sizeof(a))
#define endl "\n"
#define mod 1000000007
#define mod1 998244353
#define ff first
#define ss second
#define MAX 500005
#define N 10004
#define INF 1000000009
#define all(v) v.begin(), v.end()
#define sbit(a) __builtin_popcount(a)
template <typename T>
using ordered_set =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef pair<ll, ll> pll;
typedef pair<pll, ll> ppl;
typedef map<ll, ll> mpll;
typedef map<vector<ll>, ll> mpvl;
ll power(ll x, ll y, ll p) {
  ll res = 1;

  x = x % p;

  if (x == 0)
    return 0;
  while (y > 0) {

    if (y & 1)
      res = (res * x) % p;

    y = y >> 1;
    x = (x * x) % p;
  }

  return res;
}
void solve() {

  ll n, x, m;
  cin >> n >> x >> m;
  ll ans = x;
  ll t = x * x;
  ll c = 0;
  map<ll, ll> mp;
  n--;
  ll s[m + 1];
  mem0(s);
  ll tans = 0;
  ll tmp;
  for (ll i = 1; i <= min(n, m + 1); i++) {
    ll md = t % m;
    if (!mp.count(md)) {
      tans += md;
      t = md * md;
    } else {
      c = i - mp[md];
      tmp = mp[md];
      break;
    }
    mp[md] = i;
    s[i] = tans;
  }
  if (mp.count(0)) {
    ans += tans;
    cout << ans << endl;
    return;
  }
  tmp--;
  n -= tmp;
  ll div = n / c;
  ll md = n % c;
  ans += (div * (s[c + tmp] - s[tmp]));
  ans += s[tmp];
  ans += s[tmp + md] - s[tmp];
  cout << ans << endl;
}
int main() {
  speed;
  ll kk;
  kk = 1;
  // cin >> kk;
  while (kk--) {

    solve();
  }

  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
#include <iostream>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define speed                                                                  \
  ios_base::sync_with_stdio(0);                                                \
  cin.tie(0);                                                                  \
  cout.tie(0);
#define ll long long
#define pb push_back
#define mem1(a) memset(a, -1, sizeof(a))
#define mem0(a) memset(a, 0, sizeof(a))
#define endl "\n"
#define mod 1000000007
#define mod1 998244353
#define ff first
#define ss second
#define MAX 500005
#define N 10004
#define INF 1000000009
#define all(v) v.begin(), v.end()
#define sbit(a) __builtin_popcount(a)
template <typename T>
using ordered_set =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef pair<ll, ll> pll;
typedef pair<pll, ll> ppl;
typedef map<ll, ll> mpll;
typedef map<vector<ll>, ll> mpvl;
ll power(ll x, ll y, ll p) {
  ll res = 1;

  x = x % p;

  if (x == 0)
    return 0;
  while (y > 0) {

    if (y & 1)
      res = (res * x) % p;

    y = y >> 1;
    x = (x * x) % p;
  }

  return res;
}
void solve() {

  ll n, x, m;
  cin >> n >> x >> m;
  ll ans = x;
  ll t = x * x;
  ll c = 0;
  map<ll, ll> mp;
  n--;
  ll s[m + 1];
  mem0(s);
  ll tans = 0;
  ll tmp;
  for (ll i = 1; i <= m + 1; i++) {
    ll md = t % m;
    if (!mp.count(md)) {
      tans += md;
      t = md * md;
    } else {
      c = i - mp[md];
      tmp = mp[md];
      break;
    }
    mp[md] = i;
    s[i] = tans;
  }
  if (mp.count(0)) {
    ans += tans;
    cout << ans << endl;
    return;
  }
  tmp--;
  n -= tmp;
  ll div = n / c;
  ll md = n % c;
  ans += (div * (s[c + tmp] - s[tmp]));
  ans += s[tmp];
  ans += s[tmp + md] - s[tmp];
  cout << ans << endl;
}
int main() {
  speed;
  ll kk;
  kk = 1;
  // cin >> kk;
  while (kk--) {

    solve();
  }

  return 0;
}