CodeForces 597B Restaurant

#include<iostream>
#include<cstring>
#include<cmath>
#include<queue>
#include<algorithm>
#include<cstdio>
using namespace std;

int n;
const int maxn=500000+10;
struct X
{
    int L,R;
}s[maxn];

bool cmp(const X&a,const X&b)
{
    if(a.R==b.R) return a.L<b.L;
    return a.R<b.R;
}

int main()
{
    scanf("%d",&n);
    for(int i=1;i<=n;i++) scanf("%d%d",&s[i].L,&s[i].R);
    sort(s+1,s+1+n,cmp);
    int ans=0,pre=0;;
    for(int i=1;i<=n;i++)
    {
        if(s[i].L>pre)
        {
            pre=s[i].R;
            ans++;
        }
    }
    printf("%d\n",ans);
    return 0;
}