Go: package main

import (
	"bufio"
	"fmt"
	"math/big"
	"os"
	"strconv"
)

var sc = bufio.NewScanner(os.Stdin)

func main() {
	sc.Scan()
	dataset, _ := strconv.Atoi(sc.Text())
	var firstdata *big.Int

	for i := 0; i < dataset*2; i++ {
		n := new(big.Int)
		sc.Scan()
		data, _ := n.SetString(sc.Text(), 10)

		if i%2 == 0 {
			firstdata = data
			continue
		}

		result := new(big.Int)
		if result := result.Add(data, firstdata); len(result.String()) > 80 {
			fmt.Println("overflow")
			continue
		} else {
			fmt.Println(result)
		}
	}
}

C++: #include<iostream>
#include<stdio.h>
#include <algorithm>
#include<string>
#include <utility>
using namespace std;
using namespace std;
int main(){
	int m;
	string in,in2;
	int a[90],b[90],ans[90];
	int f;
	int a_len,b_len,m_len;
	cin>>m;
	while(m--){
		for(int i=0;i<90;i++){
			a[i]=b[i]=ans[i]=0;
		}
		cin>>in;
		cin>>in2;
		a_len=in.size();
		b_len=in2.size();
		for(int i=0;i<a_len;i++){
			a[a_len-1-i]=in[i]-'0';
		}
		for(int i=0;i<b_len;i++){
			b[b_len-1-i]=in2[i]-'0';
		}
		m_len=max(a_len,b_len);
		if(m_len>80){
			cout<<"overflow"<<endl;
			continue;
		}
		
		
	}
	
	
	return 0;
}

C++: #include <iostream>
#include <vector>
#include <string>
using namespace std;

int main(){
	string a, b;
	vector<int> ans;
	int n, num, ai, bi, c=0;
	bool flag;

	//f[^ZbgÌüÍ
	cin >> n;
	
	for(int i=0 ; i<n ; i++){
		cin >> a >> b;
		flag = false;
		
		//aðvZ·é
		for(int j=0 ; j<100 ; j++){
			num = 0;
			ai = a.size()-j-1;
			bi = b.size()-j-1;
			if( ai<0 && bi<0 && c==0) break;
			
			if(ai>=0)num += a[ ai ] - 48;
			if(bi>=0)num += b[ bi ] - 48;
			ans.push_back( (num+c)%10 );
			if(num+c >= 10) c = 1;
			else c = 0;
		}
		if(ans.size()>80){
			flag = true;
		}
		if(flag){
			printf("overflow");
		}else{
			for(int j=ans.size()-1 ; j>=0 ; --j){
				printf("%d", ans[j]);
			}
		}
		printf("\n");
		ans.clear();
	}
	return 0;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
#include <math.h>
#include <vector>
#include <set>

using namespace std;
typedef long long LL;
static const double EPS = 1e-9;

#define FOR(i,k,n) for (int i=(k); i<(int)(n); ++i)
#define REP(i,n) FOR(i,0,n) 

int main(void){  
  int n;
  cin >> n;
  REP(i,n){
    string num1s;
    string num2s;
    cin >> num1s >> num2s;
    if(num1s.size()>80||num2s.size()>80)
      cout << "overflow" << endl;
    else{
      int num1[81] = {0}, num2[81] = {0}, sum[81] = {0} ;
      REP(i,num1s.size()) num1[num1s.size()-1-i] = ( num1s[i] - '0' );
      REP(i,num2s.size()) num2[num2s.size()-1-i] = ( num2s[i] - '0' );
      REP(i,80) sum[i] = num1[i] + num2[i];
      REP(i,80) if(sum[i] > 9){
        sum[i+1] += sum[i]/10;
        sum[i] = sum[i]%10;
      }
      if(sum[80] > 9) cout << "overflow" << endl;
      else{
        int first = 79;
        while(sum[first] == 0 && first !=0) first--;
        for(int i=first; i>=0; i--)
          cout << sum[i];
        cout << endl;
      }
    }
  }
}

C++: #include<iostream>
#include<stdio.h>
#include <algorithm>
#include<string.h>
#include <utility>
using namespace std;
int main(){
	int m;
	string in1,in2;
	int a[1000],b[1000],ans[1000];
	int f;
	int alen,blen,mlen;
	cin>>m;
	while(m--){
		for(int i=0;i<90;i++){
			a[i]=b[i]=ans[i]=0;
		}
		in1="";
		in2="";
		cin>>in1;
		cin>>in2;
		alen=in1.size();
		blen=in2.size();
		for(int i=0;i<alen;i++){
			a[alen-1-i]=in1[i]-'0';
		}
		for(int i=0;i<blen;i++){
			b[blen-1-i]=in2[i]-'0';
		}
		mlen=max(alen,blen);
		if(mlen>80){
			cout<<"overflow"<<endl;
			continue;
		}
		f=0;
		for(int i=0;i<mlen+1;i++){
			ans[i]=(a[i]+b[i]+f)%10;
			f=(a[i]+b[i]+f)/10;
		}
		if(ans[mlen]!=0){
			if(mlen>79){
				cout<<"overflow"<<endl;
				continue;
			}
			cout<<ans[mlen];
		}
		
		for(int i=0;i<mlen;i++){
			cout<<ans[mlen-1-i];
		}cout<<endl;
		
		
	}
	return 0;
}

C++: #include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
using namespace std;
static const double EPS = 1e-5;
typedef long long ll;
typedef pair<int,int> pint;
#define rep(i,n) for(int i=0;i<n;i++)
#define F first
#define S second
int dx[]={1,-1,0,0},dy[]={0,0,1,-1};

int N;

int f(string s1,string s2,int x){
	if(s1.size()<=N&&s2.size()<=N&&x==0)return 0;
	if(N>80){cout<<"overflow"<<endl;return 0;}
	if(s1.size()>N)x+=s1[s1.size()-N-1]-'0';
	if(s2.size()>N)x+=s2[s2.size()-N-1]-'0';
	++N;
	f(s1,s2,x/10);
	if(N<=80)cout<<x%10;
	return 0;
}

int main(){
	int n;
	cin>>n;
	rep(i,n){
		string s1,s2;
		cin>>s1>>s2;
		f(s1,s2,0);
		cout<<endl;
	}
	return 0;
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <functional>
#include <numeric>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <utility>
#include <sstream>
#include <complex>

using namespace std;

#define FOR(i,a,b) for(long long i=(a);i<(b);i++)
#define REP(i,N) for(long long i=0;i<(N);i++)
#define ALL(s) (s).begin(),(s).end()
#define fi first
#define se second

#define PI acos(-1.0)
#define INF 1000000007

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<string, ll> PS;
typedef vector<ll> V;

/*int k = 0, n;
string s, t;
vector<string> ans;

int main(){
	cin >> n;
	REP(j,n){
		cin >> s >> t;
		k = 0;
		if (s.size() >= 80 || t.size() >= 80){
			cout << "overflow" << endl;
			continue;
		}
		reverse(ALL(s));
		reverse(ALL(t));
		int a = max(s.size(), t.size()), b = min(s.size(), t.size());
		if (s.size() > t.size()){
			REP(i, a - b){
				t += "0";
			}
		}
		else{
			REP(i, a - b){
				s += "0";
			}
		}		
		reverse(ALL(s));
		reverse(ALL(t));
		REP(i, s.size()){
			int x = (s[s.size()-1-i] - '0') + (t[s.size()-1-i] - '0');
			string q;
			stringstream ss;
			if (i != s.size() - 1){
				ss << ((x + k) % 10);
			}
			else{
				ss << x + k;
			}
			ss >> q;
			ans.push_back(q);
			if (x + k >= 10){
				k = (x + k) / 10;
			}
			else{
				k = 0;
			}
		}
		if (ans.size() >= 79){
			cout << "overflow" << endl;
			continue;
		}
		//cout << ans.size() << endl;
		reverse(ALL(ans));
		REP(i, ans.size()){
			cout << ans[i];
		}
		cout << endl;
		ans.clear();
	}
}*/

int a[110], b[110], ans[110];
string s, t;
int n;

int main(){
	cin >> n;
	while (n--){
		cin >> s >> t;
		if (s.size() > 80 || t.size() > 80){
			cout << "overflow\n";
			continue;
		}
		REP(i, s.size())a[i] = s[s.size() - 1 - i] - '0';
		REP(i, t.size())b[i] = t[t.size() - 1 - i] - '0';
		ll k = 0;
		REP(i, 101){
			ans[i] = (a[i] + b[i] + k) % 10;
			k = (a[i] + b[i] + k) / 10;
		}
		if (ans[80] != 0){
			cout << "overflow\n";
			continue;
		}
		for (int i = max(s.size(), t.size()); i >= 0; i--){
			if (i == max(s.size(), t.size())){
				if (ans[i] != 0){
					cout << ans[i];
				}
			}
			else{
				cout << ans[i];
			}
		}
		cout << endl;
		REP(i, 101){
			ans[i] = 0;
			a[i] = 0;
			b[i] = 0;
		}
	}
}