[Usaco2007 Demo][BZOJ1628] City skyline

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#include<set>
using namespace std;
int n,x,w,h[50005],ans,top,stack[50005];
int main()
{
    scanf("%d%d",&n,&w);
    ans=n; 
    for (int i=1;i<=n;i++) scanf("%d%d",&x,&h[i]);
    for (int i=1;i<=n;i++) 
    {
        while (h[i]<stack[top]) top--;
        if (h[i]==stack[top]) ans--;
            else stack[++top]=h[i];
    }
    printf("%d",ans);
    return 0;
}