Problem p03721 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bits/stdc++.h>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <string>
#include <vector>
//    #include <boost/multiprecision/cpp_int.hpp>
#include <functional>
//    #define int long long
#define inf 1000000007
#define pa pair<int, int>
#define ll long long
#define pal pair<double, pa>
#define ppa pair<pa, int>
#define ppap pair<int, pa>
#define ssa pair<string, int>
#define mp make_pair
#define pb push_back
#define EPS (1e-10)
#define equals(a, b) (fabs((a) - (b)) < EPS)

using namespace std;
// priority_queue<int, vector<int>, greater<int> > que;
class Point {
public:
  double x, y;
  Point(double x = 0, double y = 0) : x(x), y(y) {}
  Point operator+(Point p) { return Point(x + p.x, y + p.y); }
  Point operator-(Point p) { return Point(x - p.x, y - p.y); }
  Point operator*(double a) { return Point(x * a, y * a); }
  Point operator/(double a) { return Point(x / a, y / a); }
  double absv() { return sqrt(norm()); }
  double norm() { return x * x + y * y; }
  bool operator<(const Point &p) const { return x != p.x ? x < p.x : y < p.y; }
  bool operator==(const Point &p) const {
    return fabs(x - p.x) < EPS && fabs(y - p.y) < EPS;
  }
};
typedef Point Vector;

struct Segment {
  Point p1, p2;
};

double hen(Vector a) {
  if (fabs(a.x) < EPS && a.y > 0)
    return acos(0);
  else if (fabs(a.x) < EPS && a.y < 0)
    return 3 * acos(0);
  else if (fabs(a.y) < EPS && a.x < 0)
    return 2 * acos(0);
  else if (fabs(a.y) < EPS && a.x > 0)
    return 0.0;
  else if (a.y > 0)
    return acos(a.x / a.absv());
  else
    return 2 * acos(0) + acos(-a.x / a.absv());
}

string itos(int i) {
  ostringstream s;
  s << i;
  return s.str();
}

int gcd(int v, int b) {
  if (v > b)
    return gcd(b, v);
  if (v == b)
    return b;
  if (b % v == 0)
    return v;
  return gcd(v, b % v);
}
double dot(Vector a, Vector b) { return a.x * b.x + a.y * b.y; }
double cross(Vector a, Vector b) { return a.x * b.y - a.y * b.x; }

double distans(double x1, double y1, double x2, double y2) {
  double rr = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
  return sqrt(rr);
}
/*}
int pr[100010];
//int inv[100010];

int beki(int wa,int rr){
if(rr==0) return 1ll;
if(rr==1) return wa;
if(rr%2==1) return (beki(wa,rr-1)*wa)%inf;
int zx=beki(wa,rr/2);
return (zx*zx)%inf;
}

void gya(){
pr[0]=1;
for(int i=1;i<100010;i++){
pr[i]=(pr[i-1]*i)%inf;
}
for(int i=0;i<100010;i++) inv[i]=beki(pr[i],inf-2);

}

*/

//----------------kokomade tenpure------------

int a[200020] = {0};
string s, t, tt;

signed main() {
  int n, m;
  cin >> n >> m;
  for (int i = 0; i < n; i++) {
    int d, dd;
    cin >> d >> dd;
    a[d] += dd;
  }
  int u = 0, i = 1;
  while (1) {
    u += a[i];
    if (u >= m) {
      cout << i << endl;
      return 0;
    }
    i++;
  }
  //	cout<<(char)(s[0]+'A'-'a')<<(char)(t[0]+'A'-'a')<<(char)(tt[0]+'A'-'a')<<endl;
  /*
  for(int i=0;i<s.length()+t.length();i++){
          if(i%2==0) cout<<s[i/2];
          else cout<<t[i/2];
  }
  cout<<endl;
  */
  /*
  while(1){
  //	string s;
  //	int na,nb;
  cin>>s;
          if(s==".") return 0;


  }

  */

  return 0;
}


Fixed submission:
#include <algorithm>
#include <bits/stdc++.h>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <string>
#include <vector>
//    #include <boost/multiprecision/cpp_int.hpp>
#include <functional>
#define int long long
#define inf 1000000007
#define pa pair<int, int>
#define ll long long
#define pal pair<double, pa>
#define ppa pair<pa, int>
#define ppap pair<int, pa>
#define ssa pair<string, int>
#define mp make_pair
#define pb push_back
#define EPS (1e-10)
#define equals(a, b) (fabs((a) - (b)) < EPS)

using namespace std;
// priority_queue<int, vector<int>, greater<int> > que;
class Point {
public:
  double x, y;
  Point(double x = 0, double y = 0) : x(x), y(y) {}
  Point operator+(Point p) { return Point(x + p.x, y + p.y); }
  Point operator-(Point p) { return Point(x - p.x, y - p.y); }
  Point operator*(double a) { return Point(x * a, y * a); }
  Point operator/(double a) { return Point(x / a, y / a); }
  double absv() { return sqrt(norm()); }
  double norm() { return x * x + y * y; }
  bool operator<(const Point &p) const { return x != p.x ? x < p.x : y < p.y; }
  bool operator==(const Point &p) const {
    return fabs(x - p.x) < EPS && fabs(y - p.y) < EPS;
  }
};
typedef Point Vector;

struct Segment {
  Point p1, p2;
};

double hen(Vector a) {
  if (fabs(a.x) < EPS && a.y > 0)
    return acos(0);
  else if (fabs(a.x) < EPS && a.y < 0)
    return 3 * acos(0);
  else if (fabs(a.y) < EPS && a.x < 0)
    return 2 * acos(0);
  else if (fabs(a.y) < EPS && a.x > 0)
    return 0.0;
  else if (a.y > 0)
    return acos(a.x / a.absv());
  else
    return 2 * acos(0) + acos(-a.x / a.absv());
}

string itos(int i) {
  ostringstream s;
  s << i;
  return s.str();
}

int gcd(int v, int b) {
  if (v > b)
    return gcd(b, v);
  if (v == b)
    return b;
  if (b % v == 0)
    return v;
  return gcd(v, b % v);
}
double dot(Vector a, Vector b) { return a.x * b.x + a.y * b.y; }
double cross(Vector a, Vector b) { return a.x * b.y - a.y * b.x; }

double distans(double x1, double y1, double x2, double y2) {
  double rr = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
  return sqrt(rr);
}
/*}
int pr[100010];
//int inv[100010];

int beki(int wa,int rr){
if(rr==0) return 1ll;
if(rr==1) return wa;
if(rr%2==1) return (beki(wa,rr-1)*wa)%inf;
int zx=beki(wa,rr/2);
return (zx*zx)%inf;
}

void gya(){
pr[0]=1;
for(int i=1;i<100010;i++){
pr[i]=(pr[i-1]*i)%inf;
}
for(int i=0;i<100010;i++) inv[i]=beki(pr[i],inf-2);

}

*/

//----------------kokomade tenpure------------

int a[200020] = {0};
string s, t, tt;

signed main() {
  int n, m;
  cin >> n >> m;
  for (int i = 0; i < n; i++) {
    int d, dd;
    cin >> d >> dd;
    a[d] += dd;
  }
  int u = 0, i = 1;
  while (1) {
    u += a[i];
    if (u >= m) {
      cout << i << endl;
      return 0;
    }
    i++;
  }
  //	cout<<(char)(s[0]+'A'-'a')<<(char)(t[0]+'A'-'a')<<(char)(tt[0]+'A'-'a')<<endl;
  /*
  for(int i=0;i<s.length()+t.length();i++){
          if(i%2==0) cout<<s[i/2];
          else cout<<t[i/2];
  }
  cout<<endl;
  */
  /*
  while(1){
  //	string s;
  //	int na,nb;
  cin>>s;
          if(s==".") return 0;


  }

  */

  return 0;
}