Problem p03038 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#include <string>
#include <vector>
using namespace std;
typedef pair<int, int> P;
typedef long long ll;
#define rep(i, n) for (ll i = 0; i < n; ++i)
#define exrep(i, a, b) for (ll i = a; i <= b; i++)
#define out(x) cout << x << endl
#define exout(x) printf("%.10f\n", x)
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define pb push_back
#define re0 return 0
const ll MOD = 1000000007;
const ll INF = 1e16;
const ll MAX_N = 5010;
// max=({});
// 条件式が真ならwhileの中身を回し続ける
// printf("%d\n", ans);

// pairの入力
// vector<pair<ll, ll>>work(n);
// rep(i, n) {
//	ll a, b;
//	cin >> a >> b;
//	work[i] = make_pair(a, b);
// for(auto p:mp)(mapの探索)
// printf("%.10f\n",なんちゃら)
// 最大公約数
ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; }

ll lcm(ll x, ll y) {
  if (x == 0 || y == 0)
    return 0;
  return (x / gcd(x, y) * y);
}

// 組み合わせの余りを求める
ll fac[MAX_N], finv[MAX_N], inv[MAX_N];
void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAX_N; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}

// 二項係数計算
long long COM(ll n, ll k) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

ll dx[4] = {0, 0, -1, 1};
ll dy[4] = {-1, 1, 0, 0};
ll dp[101010];

// union-find木について
ll par[101010];
ll rank2[101010];

void init(ll n) {
  rep(i, n) {
    par[i] = i;
    rank2[i] = 0;
  }
}

ll find(ll x) {
  if (par[x] == x) {
    return x;
  } else {
    return par[x] = find(par[x]);
  }
}

void unite(ll x, ll y) {
  x = find(x);
  y = find(y);
  if (x == y)
    return;
  if (rank2[x] < rank2[y]) {
    par[x] = y;
  } else {
    par[y] = x;
    if (rank2[x] == rank2[y]) {
      rank2[x]++;
    }
  }
}

long long modpow(long long a, long long n, long long mod) {
  long long res = 1;
  while (n > 0) {
    if (n & 1)
      res = res * a % mod;
    a = a * a % mod;
    n >>= 1;
  }
  return res;
}

char c[2010][2010];
bool flag[2010][2010];
ll cnt[2010][2010];

// long longしか使わない
// 素数は1より大きい
int main() {
  ll n, m;
  cin >> n >> m;
  vector<ll> a(n);
  rep(i, n) { cin >> a[i]; }
  sort(a.begin(), a.end());
  vector<pair<ll, ll>> p(m);
  rep(i, m) { cin >> p[i].second >> p[i].first; }
  sort(p.rbegin(), p.rend());
  vector<ll> change;
  rep(i, m) {
    rep(j, p[i].second) {
      change.push_back(p[i].first);
      if (change.size() == n)
        break;
    }
  }
  ll k = change.size();
  if (k < n) {
    rep(i, n - k) { change.push_back(-1); }
  }
  ll ans = 0;
  rep(i, n) { ans += max(a[i], change[i]); }
  cout << ans << endl;
}

Fixed submission:
#include <bits/stdc++.h>
#include <string>
#include <vector>
using namespace std;
typedef pair<int, int> P;
typedef long long ll;
#define rep(i, n) for (ll i = 0; i < n; ++i)
#define exrep(i, a, b) for (ll i = a; i <= b; i++)
#define out(x) cout << x << endl
#define exout(x) printf("%.10f\n", x)
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define pb push_back
#define re0 return 0
const ll MOD = 1000000007;
const ll INF = 1e16;
const ll MAX_N = 5010;
// max=({});
// 条件式が真ならwhileの中身を回し続ける
// printf("%d\n", ans);

// pairの入力
// vector<pair<ll, ll>>work(n);
// rep(i, n) {
//	ll a, b;
//	cin >> a >> b;
//	work[i] = make_pair(a, b);
// for(auto p:mp)(mapの探索)
// printf("%.10f\n",なんちゃら)
// 最大公約数
ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; }

ll lcm(ll x, ll y) {
  if (x == 0 || y == 0)
    return 0;
  return (x / gcd(x, y) * y);
}

// 組み合わせの余りを求める
ll fac[MAX_N], finv[MAX_N], inv[MAX_N];
void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAX_N; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}

// 二項係数計算
long long COM(ll n, ll k) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

ll dx[4] = {0, 0, -1, 1};
ll dy[4] = {-1, 1, 0, 0};
ll dp[101010];

// union-find木について
ll par[101010];
ll rank2[101010];

void init(ll n) {
  rep(i, n) {
    par[i] = i;
    rank2[i] = 0;
  }
}

ll find(ll x) {
  if (par[x] == x) {
    return x;
  } else {
    return par[x] = find(par[x]);
  }
}

void unite(ll x, ll y) {
  x = find(x);
  y = find(y);
  if (x == y)
    return;
  if (rank2[x] < rank2[y]) {
    par[x] = y;
  } else {
    par[y] = x;
    if (rank2[x] == rank2[y]) {
      rank2[x]++;
    }
  }
}

long long modpow(long long a, long long n, long long mod) {
  long long res = 1;
  while (n > 0) {
    if (n & 1)
      res = res * a % mod;
    a = a * a % mod;
    n >>= 1;
  }
  return res;
}

char c[2010][2010];
bool flag[2010][2010];
ll cnt[2010][2010];

// long longしか使わない
// 素数は1より大きい
int main() {
  ll n, m;
  cin >> n >> m;
  vector<ll> a(n);
  rep(i, n) { cin >> a[i]; }
  sort(a.begin(), a.end());
  vector<pair<ll, ll>> p(m);
  rep(i, m) { cin >> p[i].second >> p[i].first; }
  sort(p.rbegin(), p.rend());
  vector<ll> change;
  rep(i, m) {
    rep(j, p[i].second) {
      change.push_back(p[i].first);
      if (change.size() == n)
        break;
    }
    if (change.size() == n)
      break;
  }
  ll k = change.size();
  if (k < n) {
    rep(i, n - k) { change.push_back(-1); }
  }
  ll ans = 0;
  rep(i, n) { ans += max(a[i], change[i]); }
  cout << ans << endl;
}