22 lines
584 B
C++
22 lines
584 B
C++
#include <cstdio>
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#include <algorithm>
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using namespace std;
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const int N=20010;
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struct line{int l,r;}s[N];
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int n,head,tail;
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long long ans;
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bool cmp(line a,line b){return a.l==b.l? a.r<b.r:a.l<b.l;}
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int main(){
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//freopen("1165.in","r",stdin);freopen("1165.out","w",stdout);
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scanf("%d",&n);
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for(int i=1;i<=n;i++) scanf("%d%d",&s[i].l,&s[i].r);
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sort(s+1,s+n+1,cmp);
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for(int i=1;i<n;i++){
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if(s[i].r>=s[i+1].l) s[i+1].l=s[i].l,s[i+1].r=max(s[i].r,s[i+1].r);
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else ans+=s[i].r-s[i].l;
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}
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ans+=s[n].r-s[n].l;
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printf("%lld",ans);
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return 0;
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}
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