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#include <bits/stdc++.h>

using namespace std;

#define st first
#define nd second
#define pb push_back
#define sz(x) (int)(x).size()
#define ll long long
int mod=1000000007;
int inf=1000000007;
ll infl=1000000000000000007;

int tab[3000007][2];

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n,w,t,r,ans=0;
    cin>>n;
    for(int i=1;i<=n;i++)
    {
        cin>>r>>w>>t;
        tab[w-t+1000000][r-1]++;
    }
    for(int i=0;i<=3000000;i++) ans+=min(tab[i][0],tab[i][1]);
    cout<<ans;

    return 0;
}