"use strict";
var GET=(function(){function f(s){return new g(s);}function g(s){this._s=s.trim().split("\n");this._y=0;}g.prototype.a=function(f){var s=this._s, y=this._y, r;if(typeof s[y]==="string")s[y]=s[y].split(" ").reverse();r=s[y].pop();if(!s[y].length)this._y++;return f?r:+r;};g.prototype.l=function(f){var s=this._s[this._y++].split(" ");return f?s:s.map(a=>+a);};g.prototype.m=function(n,f){var r=this._s.slice(this._y,this._y+=n).map(a=>a.split(" "));return f?r:r.map(a=>a.map(a=>+a));};g.prototype.r=function(n,f){var r=this._s.slice(this._y,this._y+=n);return f?r:r.map(a=>+a);};return f;})();
var o=GET(require("fs").readFileSync("/dev/stdin","utf8"));
function xArray(v){var a=arguments,l=a.length,r="Array(a["+--l+"]).fill(0).map(x=>{return "+v+";})";while(--l)r="Array(a["+l+"]).fill(0).map(x=>"+r+")";return eval(r);}

console.log(main());
function main(){
  var n = o.a();
  var xy = xArray(-1,n,n);
  for(var i = 0; i < n; i++){
    var a = o.a();
    for(var j = 0; j < a; j++){
      var x = o.a(), y = o.a();
      x--;
      xy[i][x] = y;
    }
  }
  var ans = 0;
  for(var i = 1; i < 1 << n; i++){
    var set = new Set();
    var j = i, k = 0, mx = 0;
    while(j){
      if(j & 1)set.add(k), mx++;
      j >>= 1;
      k++;
    }
    if(mx <= ans)continue;
    var flag = 1;
    for(var j of set){
      for(var k = 0; k < n && flag; k++){
        var t = xy[j][k];
        if(t === -1)continue;
        if(t === 1 && set.has(k))continue;
        if(t === 0 && !set.has(k))continue;
        flag = 0;
      }
    }
    if(flag)ans = mx;
  }
  return ans;
}