Submission #2247360

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Source Code Expand

// luogu-judger-enable-o2
#pragma GCC optimize(3)
#include<bits/stdc++.h>
using namespace std;
int k=1;
bool visit[10005];
int main() {
    int N;
    scanf("%d",&N);
    if(N<2)return printf("0\n"),0;
    if(N==3)return printf("1\n"),0;
    int kkk=sqrt(N);
    for(int i=4;i<=N;i+=2){
        visit[i]=1;
    }
    for(register int i=3; i<=kkk; i+=2) {
        if(!visit[i]) {
            k++;
            for(register int j=i+i; j<=N; j+=i) {
                visit[j]=1;
            }
        }
    }
    for(int i=kkk+1; i<=N; i++) {
        if(!visit[i])k++;
    }
    printf("%d\n",visit[N]?k:k-1);
    return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:9:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&N);
                   ^

Judge Result