const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;
void async function () {
// Write your code here
await readline()
const map = new Map()
let key = 0
let value = 0
while(line = await readline()) {
const arr = line.split(" ")
key = Number(arr[0]), value = Number(arr[1])
map.set(key,(map.get(key) || 0) + value)
}
const res = Array.from(map.entries()).sort((a,b) => a[0] - b[0])
res.forEach((value) => {
console.log(value[0],value[1])
})
}()
