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: times=int(input())
for i in range(times):
    a=int(input())
    b=int(input())
    if len(str(a))<80 or len(str(b))<80 or len(str(a+b))<80:
        print(a+b)
    else: print("overflow")

Python: for i in range(int(input())):
    a, b = int(input()), int(input())
    result = a+b if len(str(a+b))<=80 else 'overflow'
    print(result)

Python: for _ in range(int(input())):
    a = int(input())
    b = int(input())
    s = a + b
    if s >= 10 ** 80:
        print('overflow')
    else:
        print(s)

Python: N = 10**80
for i in range(int(input())):
	n = int(input()) + int(input())
	print(n if n < N else "overflow")

Python: n = int(input())
for i in range(n):
	x = int(input())
	y = int(input())
	ans = x + y
	if(ans < 10**80):
		print(ans)
	else:
		print("overflow")

Python: # National Budget
md = 80
for _ in range(int(input())):
    a,b = int(input()),int(input())
    ab = a + b
    if a >= pow(10,md) or b >= pow(10,md) or ab >= pow(10,md):
        print('overflow')
    else:
        print(a+b)

Python: num = int(input())

for i in range(num):
    total = int(input()) + int(input())
    if len(str(total)) > 80:
        print("overflow")
    else:
        print(total)

Python: for i in range(int(input())):
    try:
        a = int32(sum([int32(j) for j in input().split()]))
    except:
        print("overflow")
    else:
        print(a)

Python: n = int(input())
for i in range(n):
    s = int(input()) + int(input())
    if len(str(s)) <= 80:
        print(s)
    else:
        print('overflow')

Python: n = int(input())
for i in range(n):
    x = input()
    y = input()
    if len(x) > 80 or len(y) > 80:
        print("overflow")
        continue
    s = ""
    rx = x[::-1]
    ry = y[::-1]
    lx = len(x)
    ly = len(y)
    if lx > ly:
        ml = lx
    else:
        ml = ly
    c = 0
    for j in range(ml + 1):
        x1 = 0
        y1 = 0
        if j < lx:
            x1 = int(rx[j])
        if j < ly:
            y1 = int(ry[j])
        c1 = x1 + y1 + c
        s += str(c1 % 10)
        c = c1 // 10

    rs = s[::-1]
    result = ""
    for j in range(len(rs)):
        if rs[j] != "0":
            result = rs[j:]
            break

    if len(result) > 80:
        print("overflow")
    elif result == "":
        print(0)
    else:
        print(result)

Python: import sys
f = sys.stdin
n = int(f.readline())
for _ in range(n):
    a = f.readline().strip()
    b = f.readline().strip()
    c = int(a) + int(b)
    c = '{}'.format(c)
    print(c if len(c) else 'overflow ')

Python: import math

def calc_digit(data1, data2):
    if(data1 == 0):
        data_size2 = int(len(str(data2)))
        data_size1 = 1
    elif(data2 == 0):
        data_size1 = int(len(str(data2)))
        data_size2 = 1
    else:
        data_size1 = int(len(str(data1)))
        data_size2 = int(len(str(data2)))
    return(data_size1, data_size2)

def two_number_sum(data1, data2):
    result = data1 + data2
    if int(len(str(result))) > 80:
        print("overflow")
    else:
        print(result)

def main():
    a = []
    N = int(input())
    for i in range(N*2):
        a.append(input())
    for i in range(0, N*2):
        if i % 2 == 0:
            continue
        else:
            data1 = int(a[i-1])
            data2 = int(a[i])
            if(data1 == None):
                data1 = 0
            elif(data2 == None):
                data2 = 0
            x, y = calc_digit(data1, data2)
            if(x > 80 or y > 80):
                print("overflow")
                continue
            two_number_sum(data1, data2)

if __name__ == '__main__':
    main()

Python: import sys
import re
def line():return sys.stdin.readline().strip()

N = input()
while True:
    try:
        a = int(line())
        b = int(line())
        if a + b >= 10 ** 80:
            print("overflow")
        else:
            print(a + b)
    except:
        break

Python: max = 10 ** 80
for i in range(int(input())):
    total = int(input()) + int(input())
    print(total if total < max else "overflow")

Python: N = int(input())
for _ in range(N):
    a = int(input())
    b = int(input())
    c = a + b
    length = len(str(c))
    print([c, "overflow"][length > 80])

Python: 
if __name__ == '__main__':
    n = (int)(input())
    for _ in range(n):
        sNumber = (int)(input())
        tNumber = (int)(input())
        uNumber = sNumber+tNumber
        print("over flow" if uNumber >= 10**80 else uNumber)