#include <bits/stdc++.h>
using namespace std;
int main()
{
int n;cin>>n;
map<int,int> a;
while(n--){
int b,c;cin>>b>>c;
a[b]+=c;
}
for(auto [k,v]:a)cout<<k<<" "<<v<<endl;
return 0;
}
#include <bits/stdc++.h>
using namespace std;
int main()
{
int n;cin>>n;
map<int,int> a;
while(n--){
int b,c;cin>>b>>c;
a[b]+=c;
}
for(auto [k,v]:a)cout<<k<<" "<<v<<endl;
return 0;
}