#include<bits/stdc++.h>
using namespace std;
const int N = 2e5+100, M = 1e6+100;
int cnt[M];
int main(){
ios_base::sync_with_stdio(false);cin.tie(NULL);
int n;cin >> n;
for(int i=0 ; i<n ; i++){
int m;cin >> m;
while(m --){
int l, r;cin >> l >> r;l --;
cnt[l] ++;
cnt[r] --;
}
}
int sum=0;
for(int i=0 ; i<M ; i++){
sum += cnt[i];
if(!sum){
cout << i+1 << "\n";
return 0;
}
}
cout << "-1\n";
}
{"html5":"htmlmixed","css":"css","javascript":"javascript","php":"php","python":"python","ruby":"ruby","lua":"text\/x-lua","bash":"text\/x-sh","go":"go","c":"text\/x-csrc","cpp":"text\/x-c++src","diff":"diff","latex":"stex","sql":"sql","xml":"xml","apl":"apl","asterisk":"asterisk","c_loadrunner":"text\/x-csrc","c_mac":"text\/x-csrc","coffeescript":"text\/x-coffeescript","csharp":"text\/x-csharp","d":"d","ecmascript":"javascript","erlang":"erlang","groovy":"text\/x-groovy","haskell":"text\/x-haskell","haxe":"text\/x-haxe","html4strict":"htmlmixed","java":"text\/x-java","java5":"text\/x-java","jquery":"javascript","mirc":"mirc","mysql":"sql","ocaml":"text\/x-ocaml","pascal":"text\/x-pascal","perl":"perl","perl6":"perl","plsql":"sql","properties":"text\/x-properties","q":"text\/x-q","scala":"scala","scheme":"text\/x-scheme","tcl":"text\/x-tcl","vb":"text\/x-vb","verilog":"text\/x-verilog","yaml":"text\/x-yaml","z80":"text\/x-z80"}