记录编号	152552	评测结果	AAAAAAAAAAAAAAAAAAAAA
题目名称	[HAOI 2014]贴海报	最终得分	100
用户昵称	Asm.Def	是否通过	通过
代码语言	C++	运行时间	0.007 s
提交时间	2015-03-14 23:15:17	内存使用	0.33 MiB

#include <cctype>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <vector>
#include <cstdlib>
#include <ctime>
#include <set>
using namespace std;
#ifdef DEBUG
FILE *in = fopen("test.txt", "r");
//#define in stdin
#define out stdout
#else
FILE *in = fopen("ha14d.in", "r");
FILE *out = fopen("ha14d.out", "w");
#endif
#define getc() fgetc(in)
template<class T>inline void getd(T &x){
	char ch = getc();bool neg = false;
	while(ch != '-' && !isdigit(ch))ch = getc();
	if(ch == '-')neg = true, ch = getc();
	x = ch - '0';
	while(isdigit(ch = getc()))x = x * 10 - '0' + ch;
	if(neg)x = -x;
}
/******************************************************************/
const int maxn = 1002;
bool vis[maxn];
struct Eve{
	int loc, id;
	bool beg;
	inline bool operator < (const Eve &b)const{return loc < b.loc;}
}E[maxn<<1], *End = E;

int N, M;

inline void init(){
	getd(N), getd(M);
	int i, A, B;
	for(i = 0;i < M;++i){
		getd(A), getd(B);
		End->loc = A, End->id = i, End->beg = true;++End;
		End->loc = B + 1, End->id = i, End->beg = false;++End;
	}
	sort(E, End);
}
#include <functional>
set<int, greater<int> > S;
inline void work(){
	int Ans = 0, loc = E->loc;
	Eve *it = E;
	while(it < End){
		while(it < End && it->loc == loc){
			if(it->beg)S.insert(it->id);
			else S.erase(S.find(it->id));
			++it;
		}
		if(!S.empty())vis[*S.begin()] = true;
		loc = it->loc;
	}
	for(int i = 0;i < M;++i)if(vis[i]) ++Ans;
	fprintf(out, "%d\n", Ans);
}

int main(){
	init();
	work();
	#ifdef DEBUG
		//printf("\n%.2lfsec\n", (double)clock() / CLOCKS_PER_SEC);
	#endif
	return 0;
}