Submission #65015211

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Source Code Expand

//People who believe in miracles are as amazing as miracles themselves.
#include<bits/stdc++.h>
#define ll long long
using namespace std;
inline ll read(){
    ll x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-') f=-f;ch=getchar();}
    while(ch>='0'&&ch<='9')x=(x<<3)+(x<<1)+(ch^48),ch=getchar();
    return x*f;
}

const int N=1e6+10;
int n,m; ll ans; map<pair<int,int>,int> mp;

inline void solve(){
    n=read(),m=read();
    for(int i=1;i<=m;++i){
        int x=read(),y=read(),p=(x+y)/2;
        if((x+y)&1){
            if(n&1){
                p=(x+y+n)/2,p=(p-1)%n+1;
                mp[make_pair(p,p)]++;
            }
            else{
                if(p>n/2) p-=n/2;
                mp[make_pair(p,p+1)]++;
            }
        }
        else{
            if(!(n&1)){
                if(p>n/2) p-=n/2;
            }
            mp[make_pair(p,p)]++;
        }
    }
    ans=(ll)m*(m-1)/2;
    for(auto [_,num]:mp) ans-=(ll)num*(num-1)/2;
    printf("%lld\n",ans);
}

signed main(){
#ifndef ONLINE_JUDGE
    freopen("../1.in","r",stdin);
    freopen("../1.out","w",stdout);
#endif
    return solve(),0;
}

Submission Info

Judge Result