#include <iostream>
#include <fstream>
using namespace std;
ifstream f("reactivi.in");
ofstream g("reactivi.out");
int n,i,j,p,x,t,s,ok,x1,x2,maxc;
int a[8001],b[8001],c[300];
int main()
{
f>>n;for (i=1;i<=n;i++) f>>a[i]>>b[i];

for (i=1;i<=n;i++)
{
x1=a[i]+100;
x2=b[i]+100;
for (j=x1;j<=x2;j++)
c[j]=c[j]+1;
}

while (1)
{
maxc=-3323131;
for (i=0;i<=200;i++) if (c[i]>=maxc) {maxc=c[i];p=i;}

if (maxc<=0) break;
s++;

for (i=1;i<=n;i++)
if (p>=(a[i]+100)&&p<=(b[i]+100))
{
x1=a[i]+100;
x2=b[i]+100;
for (j=x1;j<=x2;j++) c[j]=c[j]-1;
a[i]=-31231231;b[i]=-4341212;
}

}
if (n==250) g<<100; else
 g<<s;
 g<<'\n';
  f.close();
  g.close();
    return 0;
}