URAL 1203 Scientific Conference dp？贪心

题目：click here

分明就是贪心怎么会在dp的专题

 #include <bits/stdc++.h>
 using namespace std;
 typedef unsigned long long ll;
 const int INF = 0x3f3f3f3f;
 const int M = 1e5+;

 struct Node
 {
     int F, S;
     bool operator < ( const Node x ) const {
         return S < x.S;
     }
 } p[M];

 int n;
 int main()  {
     while( ~scanf("%d", &n ) )  {
         for( int i=; i<n; i++ )
             scanf("%d%d", &p[i].F, &p[i].S );
         sort( p, p+n );
         int pre = ;
         int ans = ;
         for( int i=; i<n; i++ )    {
             if( p[i].F > pre ){
                 ans++;
                 pre = p[i].S;
             }
         }
         printf("%d\n", ans );
     }
     return ;
 }