Buggy python submission (verdict: Runtime Error):
class RollingHash():
    def __init__(self,s):
        self.n=n=len(s)
        self.b=b=129
        self.M=M=2**61-1
        x,y=1,0
        self.f=f=[x]*(n+1)
        self.h=h=[y]*(n+1)
        for i,c in enumerate(s.encode()):
            f[i+1]=x=x*b%M
            h[i+1]=y=(y*b+c)%M
    def get(self,l,r):
        return(self.h[r]-self.h[l]*self.f[r-l])%self.M
def check(x):
    d={}
    for i in range(0,n-x+1):
        k=s.get(i,i+x)
        if k in d:
            if d[k]+x<=i:
                return True
        else:
            d[k]=j
    return False
n=int(input())
s=RollingHash(input())
ok,ng=0,n
while ng-ok>1:
    mid=ok+ng>>1
    if check(mid):
        ok=mid
    else:
        ng=mid
print(ok)

Fixed submission:
from subprocess import*
with open('e.cpp','w')as f:f.write(r"""
#include<iostream>
using namespace std;
main(){
  int n;
  string s;
  cin>>n>>s;
  int a=0;
  for(int i=0;i<n;++i){
    int t=0;
    for(int j=0;j<n-i;++j){
      t=(t+1)*(s[j]==s[j+i]);
      a=max(a,min(t,i));
    }
  }
  cout<<a;
}""")
call(('g++','e.cpp'))
call('./a.out')

Buggy python submission (verdict: Time Limit Exceeded):
class RollingHash():
    def __init__(self,s):
        self.n=n=len(s)
        self.b=b=129
        self.M=M=2**61-1
        x,y=1,0
        self.f=f=[x]*(n+1)
        self.h=h=[y]*(n+1)
        for i,c in enumerate(s.encode()):
            f[i+1]=x=x*b%M
            h[i+1]=y=(y*b+c)%M
    def get(self,l,r):
        return(self.h[r]-self.h[l]*self.f[r-l])%self.M
def main():
    n=int(input())
    s=RollingHash(input())
    for i in range(1,n):
        d={}
        for j in range(0,n-i+1):
            k=s.get(j,j+i)
            if k in d:
                if d[k]+i<=j:
                    break
            else:
                d[k]=j
        else:
            print(i-1)
            break
main()

Fixed submission:
from subprocess import*
with open('e.cpp','w')as f:f.write(r"""
#include<iostream>
using namespace std;
main(){
  int n;
  string s;
  cin>>n>>s;
  int a=0;
  for(int i=0;i<n;++i){
    int t=0;
    for(int j=0;j<n-i;++j){
      t=(t+1)*(s[j]==s[j+i]);
      a=max(a,min(t,i));
    }
  }
  cout<<a;
}""")
call(('g++','e.cpp'))
call('./a.out')

Buggy python submission (verdict: Time Limit Exceeded):
class RollingHash():
    def __init__(self,s):
        self.n=n=len(s)
        self.b=b=129
        self.M=M=2**61-1
        self.f=f=[1]*(n+1)
        self.h=h=[0]*(n+1)
        for i,c in enumerate(s.encode()):
            f[i+1]=f[i]*b%M
            h[i+1]=(h[i]*b+c)%M
    def get(self,l,r):
        return(self.h[r]-self.h[l]*self.f[r-l])%self.M
n=int(input())
s=RollingHash(input())
for i in range(1,n):
    d={}
    for j in range(0,n-i+1):
        k=s.get(j,j+i)
        if k in d:
            if d[k]+i<=j:
                break
        else:
            d[k]=j
    else:
        print(i-1)
        break

Fixed submission:
from subprocess import*
with open('e.cpp','w')as f:f.write(r"""
#include<iostream>
using namespace std;
main(){
  int n;
  string s;
  cin>>n>>s;
  int a=0;
  for(int i=0;i<n;++i){
    int t=0;
    for(int j=0;j<n-i;++j){
      t=(t+1)*(s[j]==s[j+i]);
      a=max(a,min(t,i));
    }
  }
  cout<<a;
}""")
call(('g++','e.cpp'))
call('./a.out')

Buggy python submission (verdict: Time Limit Exceeded):
n,s=open(0);a=i=j=0
while j<1e7:f=s[i:j]in s[j:];a=max(a,j*f-i);j+=f;i+=f^1
print(a)

Fixed submission:
from subprocess import*
with open('e.cpp','w')as f:f.write(r"""
#include<iostream>
using namespace std;
main(){
  int n;
  string s;
  cin>>n>>s;
  int a=0;
  for(int i=0;i<n;++i){
    int t=0;
    for(int j=0;j<n-i;++j){
      t=(t+1)*(s[j]==s[j+i]);
      a=max(a,min(t,i));
    }
  }
  cout<<a;
}""")
call(('g++','e.cpp'))
call('./a.out')

Buggy python submission (verdict: Time Limit Exceeded):
n,s=open(0);a=i=j=0
while j<3e7:f=s[i:j]in s[j:];a=max(a,j*f-i);j+=f;i+=f^1
print(a)

Fixed submission:
from subprocess import*
with open('e.cpp','w')as f:f.write(r"""
#include<iostream>
using namespace std;
main(){
  int n;
  string s;
  cin>>n>>s;
  int a=0;
  for(int i=0;i<n;++i){
    int t=0;
    for(int j=0;j<n-i;++j){
      t=(t+1)*(s[j]==s[j+i]);
      a=max(a,min(t,i));
    }
  }
  cout<<a;
}""")
call(('g++','e.cpp'))
call('./a.out')

Buggy python submission (verdict: Runtime Error):
n,s=open(0);a=i=j=0
while j<int(n):
 if s[l:j]in s[j:]:a=max(a,j-i);j+=1
 else:i+=1
print(a)

Fixed submission:
from subprocess import*
with open('e.cpp','w')as f:f.write(r"""
#include<iostream>
using namespace std;
main(){
  int n;
  string s;
  cin>>n>>s;
  int a=0;
  for(int i=0;i<n;++i){
    int t=0;
    for(int j=0;j<n-i;++j){
      t=(t+1)*(s[j]==s[j+i]);
      a=max(a,min(t,i));
    }
  }
  cout<<a;
}""")
call(('g++','e.cpp'))
call('./a.out')

Buggy python submission (verdict: Time Limit Exceeded):
n,s=open(0)
n=int(n)
a=0
for i in range(n):
  t=0
  for v,w in zip(s,s[i:n]):
    t=-~t*(v==w)
    if t>i:break
    if t>a:a=t
print(a)

Fixed submission:
from subprocess import*
with open('e.cpp','w')as f:f.write(r"""
#include<iostream>
using namespace std;
main(){
  int n;
  string s;
  cin>>n>>s;
  int a=0;
  for(int i=0;i<n;++i){
    int t=0;
    for(int j=0;j<n-i;++j){
      t=(t+1)*(s[j]==s[j+i]);
      a=max(a,min(t,i));
    }
  }
  cout<<a;
}""")
call(('g++','e.cpp'))
call('./a.out')

Buggy python submission (verdict: Time Limit Exceeded):
n,s=open(0)
n=int(n)
a=0
for i in range(n):
  t=0
  for v,w in zip(s,s[i:n]):
    t=-~t*(v==w)
    a=max(a,min(t,i))
print(a)

Fixed submission:
from subprocess import*
with open('e.cpp','w')as f:f.write(r"""
#include<iostream>
using namespace std;
main(){
  int n;
  string s;
  cin>>n>>s;
  int a=0;
  for(int i=0;i<n;++i){
    int t=0;
    for(int j=0;j<n-i;++j){
      t=(t+1)*(s[j]==s[j+i]);
      a=max(a,min(t,i));
    }
  }
  cout<<a;
}""")
call(('g++','e.cpp'))
call('./a.out')