#include <stdio.h>

 #include <iostream>

 #include <algorithm>

 #include <string.h>

 #include <math.h>

 #include <map>

 #include <limits.h>

 using namespace std;

 typedef long long ll;

 const int maxn = 5e5+;

 int par[maxn];

 int l[maxn],r[maxn];

 bool vis[maxn];

 void init(int n_)

 {

     for(int i=;i<=n_;i++)

     {

         par[i] = i;

         l[i] = r[i] = i;

     }

     memset(vis,false,sizeof(vis));

 }

 int find(int x)

 {

     if(x!=par[x])

     {

         return par[x] = find(par[x]);

     }

     return x;

 }

 void unite(int x,int y)

 {

     x = find(x);

     y = find(y);

     if(x==y) return ;

     par[x] = y;

     l[y] = min(l[y],l[x]);

     r[y] = max(r[y],r[x]);

     return ;

 }

 void make(int x,int y)

 {

     int pre = x;

     for(int i=x;i<y;i==r[find(i)]?i++:i=r[find(i)])

     {

         //cout<<i<<r[i]<<endl;

         if(vis[i])

         {

             pre = i;

             continue;

         }

         vis[i] = true;

         unite(pre,x);

         pre = i;

     }

 }

 int main()

 {

     int n;

     int lim = *;

     while(scanf("%d",&n)!=EOF)

     {

         init(lim);

         int L = ,R = ,a,b,c,d;

         for(int i=;i<n;i++)

         {

             scanf("%d:%d      %d:%d",&a,&b,&c,&d);

             L = a*+b;

             R = c*+d;

             make(L,R);

         }

         int ans = ;

         for(int i=;i<lim;i++)

         {

             if(false==vis[i]) ans++;

         }

         printf("%d\n",ans);

     }

     return ;

 }