JS版

let line = parseInt(readline());
const obj = {};
for(let i = 0 ; i<line ; i++){
     const arr = readline().split(" ");
     if(obj.hasOwnProperty(arr[0])) {
         obj[arr[0]] = Number(obj[arr[0]])  + Number(arr[1]);
     } else {
         obj[arr[0]] = arr[1];
     }
}

for([key , value] of Object.entries(obj)){
    console.log(key + " " + value);
}