Go: package main

import (
        "fmt"
        "bufio"
        "os"
)

func main() {
        var n int
        var a, b string
        sc := bufio.NewScanner(os.Stdin)
        fmt.Scanf("%d", &n)
        for i := 0; i < n; i++ {
                sc.Scan()
                a = sc.Text()
                sc.Scan()
                b = sc.Text()

                if len(a) > len(b) {
                        s := add(a, b)
                        if s[len(a)] > 0 {
                                if len(a) >= 80 {
                                        fmt.Printf("overflow")
                                } else {
                                        for i := 0; i <= len(a);i++ {
                                                fmt.Printf("%d", s[len(a)-i])
                                        }
                                }
                                fmt.Printf("\n")
                        } else {
                                if len(a)-1 >= 80 {
                                        fmt.Printf("overflow")
                                } else {
                                        for i := 0; i < len(a);i++ {
                                                fmt.Printf("%d", s[len(a)-i-1])
                                        }
                                }
                                fmt.Printf("\n")
                        }
                } else {
                        s := add(b, a)
                        if s[len(b)] > 0 {
                                if len(b) >= 80 {
                                        fmt.Printf("overflow")
                                } else {
                                        for i := 0; i <= len(b);i++ {
                                                fmt.Printf("%d", s[len(b)-i])
                                        }
                                }
                                fmt.Printf("\n")
                        } else {
                                if len(b)-1 >= 80 {
                                        fmt.Printf("overflow")
                                } else {
                                        for i := 0; i < len(b);i++ {
                                                fmt.Printf("%d", s[len(b)-i-1])
                                        }
                                }
                                fmt.Printf("\n")
                        }
                }
        }
}

// expects ln > lm
func add(n string, m string) (s [100]int) {
        ln := len(n)
        lm := len(m)
        var sum [100]int

        for i := 0; i < ln; i++ {
                var s, t int
                s = int(n[ln-1-i]) - int('0')

                if lm - 1 - i >= 0 {
                        t = int(m[lm-1-i]) - int('0')
                } else {
                        t = 0
                }

                sum[i+1] = (s + t + sum[i]) / 10
                sum[i] = (s + t + sum[i]) % 10
        }

        return sum
}

Python: N = int(input())
import re
for _ in [0]*N:
    a = tuple(map(int, input().zfill(100)))
    b = tuple(map(int, input().zfill(100)))
    result = []
    prev = 0
    for i in range(1, 80):
        n = int(a[-i]) + int(b[-i]) + prev
        result.append(n%10)
        prev = n // 10
    if a[-81] + b[-81] + prev > 0:
        print("overflow")
    else:
        print(re.sub(r"^0+", "", "".join(map(str, result[::-1]))))

Python: def overflow(s):
    if len(s) > 80:
        print('overflow')
    else: 
        print(s)

def string_sum(la, lb):
    d = abs(len(la) - len(lb))
    if len(la) > len(lb):
        lb = "0" * d + lb
    else:
        la = "0" * d + la
    ls = []
    carry = 0
    for a, b in zip(la[::-1], lb[::-1]):
        s = int(a) + int(b) + carry
        ls.append(str(s % 10))
        carry = s // 10
    if carry == 1:
        ls.append('1')
    return ''.join(ls[::-1])

n = int(input()) 
while n > 0:
    one = input()
    two = input()
    overflow(string_sum(one, two))
    n -= 1

Python: N = int(input())
import re
for _ in [0]*N:
    a = tuple(map(int, input().zfill(100)))
    b = tuple(map(int, input().zfill(100)))
    result = []
    prev = 0
    for i in range(1, 81):
        n = int(a[-i]) + int(b[-i]) + prev
        result.append(n%10)
        prev = n // 10
    if a[-81] + b[-81] + prev > 0:
        print("overflow")
    else:
        print(re.sub(r"^0+", "", "".join(map(str, result[::-1]))))

Python: import math

n1 = input();
n2 = input();
sum = int(n1) + int(n2);

if int(math.log10(sum)) + 1 >= 80 :
	print("overflow");
else :
	print(sum)

Python: n = int(raw_input())
for _ in [0]*n:
  a = int(raw_input())
  b = int(raw_input())
  c = a+b
  print [c,"overflow"][len(str(c))>80]

Python: def digits(n):
    if n < 10: return 1
    c = 0
    while n > 0:
        c += 1
        n = n // 10

    return c

n = int(input())
for i in range(n):
    u = int(input())
    v = int(input())
    s = u + v
    if (digits(u) > 80 or digits(v) > 80 or digits(s) > 80):
        print("overflow")
    else:
        print(s)

Python: n = int(input())
for i in range(n):
    a = int(input())
    b = int(input())
    s = a + b
    if len(str(s)) > 80 :
        print("overflow")
    else:
        print(s)

Python: from decimal import Decimal


n = int(input())
for _ in range(n):
    a = Decimal(input())
    b = Decimal(input())
    s = a + b
    s = str(s)
    if len(s) > 80:
        print("overflow")
    else:
        print(s)

Python: n = int(input())
for i in range(n):
  a = int(input())
  b = int(input())
  if len(str(a+b)) > 80:
    print("overflow")
  else:
    print(a+b)

Python: while True:
    n = int(input())
    for _ in range(n):
        a, b = int(input()), int(input())
        x = str(a+b)
        print('overflow' if len(x) > 80 else a+b)

Python: N = int(input())
import re
for _ in [0]*N:
    a = input().zfill(100)
    b = input().zfill(100)
    result = []
    prev = 0
    for i in range(1, 81):
        n = int(a[-i]) + int(b[-i]) + prev
        result.append(n%10)
        prev = n // 10
    if prev > 0 or int(a[:-80]) + int(b[:-80]) > 0:
        print("overflow")
    else:
        result = "".join(map(str, result[::-1]))
        print(int(result))

Python: import math
n=int(input())
s=[int(input()) for _ in range(n*2)]
for i in range(n):
  a=s[i*2]+s[i*2+1]
  st=str(a)
  if len(st)>80:
    print("overflow")
  else:
    print(a)

Python: # -*- coding:utf-8 -*-
N = int(input())
data1 = []
data2 = []
for i in range(N):
    data1.append(int(input()))
    data2.append(int(input()))

for i in range(N):
    if data1[i] > 10**80-1 or data2[i] > 10**80-1 or data1[i]+data2[i] > 10**80-1:
        print('overflow')
    else:
        print(data1[i]+data2[i])

Python: N = int(input())
A = []
B = []
for i in range(N):
    a = int(input())
    b = int(input())
    A.append(a)
    B.append(b)

for i in range(N):
    if A[i] >= 10 ** 80 or B[i] >= 10 ** 80:
        print("overflow")
    elif A[i] + B[i] >= 10 ** 80:
        print("overflow")
    else:
        print(str(A[i] + B[i]))

Python: # coding:utf-8
for i in range(int(input())):
	a,b =int(input()),int(input())
	if a>=pow(10,80) or b>=pow(10,80):
		print("overflow")
	else:
		big = a+b
		if big >= pow(10,80):
			print("overflow")
		else:
			print(big);

Python: n = int(input())
for _ in range(n):
    a = input()
    b = input()
    m = max(len(a), len(b))
    if m > 80:
        print("overflow")
    a = list(reversed(a))
    b = list(reversed(b))
    t = 0
    ans = []
    for i in range(m):
        try:
            num_a = int(a[i])
        except:
            num_a = 0
        try:
            num_b = int(b[i])
        except:
            num_b = 0
        s = num_a + num_b + t
        if s >= 10:
            t = 1
            s -= 10
            ans.insert(0, s)
        else:
            ans.insert(0, s)
            t = 0
    if t == 1:
        ans.insert(0, 1)
    if len(ans) > 80:
        print("overflow")
    else:
        print(*ans, sep="")