20 lines
348 B
C++
20 lines
348 B
C++
#include<cstdio>
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#include<cstring>
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bool board[10005];
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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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int a,b;
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memset(board,1,sizeof(board));
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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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memset(board+a,0,b-a+1);
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}
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int ans=0;
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for(int i=0;i<=L;i++) ans+=board[i];
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printf("%d\n",ans);
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return 0;
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}
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