20 lines
308 B
C++
20 lines
308 B
C++
#include<cstdio>
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using namespace std;
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int main()
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{
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int l,m;
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scanf("%d%d",&l,&m);
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bool road[l+1];
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for(int i=0;i<=l;i++) road[i]=1;
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int a,b,ans=0;
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for(int i=0;i<m;i++)
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{
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scanf("%d%d",&a,&b);
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for(int j=a;j<=b;j++) road[j]=0;
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}
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for(int i=0;i<=l;i++) ans+=road[i];
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printf("%d\n",ans);
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return 0;
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}
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