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#include<bits/stdc++.h>

typedef long long ll;
typedef std::pair<ll, ll> pll;
typedef std::pair<int, int> pii;

#define all(x) (x).begin(),(x).end()
#define debug std::cout<<"ok"<<std::endl

main ()
{
    int n;
    std::cin>>n;
    std::vector<std::vector<int> > V(2000001, {0,0});
    while(n--)
    {
        int a,b,c;
        std::cin>>a>>b>>c;
        V[b-c+1000000][a-1]++;
    }
    int W=0;
    for (auto a:V)
        W+=std::min(a[0], a[1]);
    std::cout<<W<<std::endl;
}