#include 
#include 
#include 
using namespace std;

int main()
{
    long long a,b;
    cin>>a>>b;
    vector>v;
    long long x,y;
    for(long long i=0;i>x>>y;
        v.push_back({x,y});
    }
    sort(v.begin(),v.end());
    long long z[a];
    long long zbir=0;
    for(long long i=0;i=b)
            {
                r=mid-1;
            }
            else
            {
                najgolem=mid;
                l=mid+1;
            }
        }
        if(najgolem + 1 < a && v[najgolem+1].first-v[i].first0)
        maxvalue=max(maxvalue, (z[najgolem]-z[i-1]));
        else if(i==0)
        maxvalue=max(maxvalue, z[najgolem]);
    }
    cout<