Problem p03545 (python)

Fixed submission:
import math
import sys
input = sys.stdin.readline

abcd = int(input())
for i in range(int(4-math.log10(abcd))):
    abcd = '0'+str(abcd)
a, b, c, d = str(abcd)
a = int(a);b = int(b);c = int(c);d = int(d)
if a+b+c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'+'+b+'+'+c+'+'+d+'=7'
elif a+b+c-d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'+'+b+'+'+c+'-'+d+'=7'
elif a+b-c-d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'+'+b+'-'+c+'-'+d+'=7'
elif a+b-c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'+'+b+'-'+c+'+'+d+'=7'
elif a-b+c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'+'+c+'+'+d+'=7'
elif a-b+c-d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'+'+c+'-'+d+'=7'
elif a-b-c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'-'+c+'+'+d+'=7'
else:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'-'+c+'-'+d+'=7'
print(ans)

Buggy submission (verdict: Runtime Error):
import sys
input = sys.stdin.readline

abcd = int(input())
a, b, c, d = str(abcd)
a = int(a);b = int(b);c = int(c);d = int(d)
if a+b+c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'+'+b+'+'+c+'+'+d+'=7'
elif a+b+c-d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'+'+b+'+'+c+'-'+d+'=7'
elif a+b-c-d == 7:
     a = str(a);b = str(b);c = str(c);d = str(d)
     ans = a+'+'+b+'-'+c+'-'+d+'=7'
elif a+b-c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'+'+b+'-'+c+'+'+d+'=7'
elif a-b+c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'+'+c+'+'+d+'=7'
elif a-b+c-d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'+'+c+'-'+d+'=7'
elif a-b-c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'-'+c+'+'+d+'=7'
else:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'-'+c+'-'+d+'=7'
print(ans)

Buggy submission (verdict: Runtime Error):
import sys
input = sys.stdin.readline

a, b, c, d = input()
ans = 0
a = int(a);b = int(b);c = int(c);d = int(d)
if a+b+c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'+'+b+'+'+c+'+'+d+'=7'
elif a+b+c-d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'+'+b+'+'+c+'-'+d+'=7'
elif a+b-c-d == 7:
     a = str(a);b = str(b);c = str(c);d = str(d)
     ans = a+'+'+b+'-'+c+'-'+d+'=7'
elif a+b-c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'+'+b+'-'+c+'+'+d+'=7'
elif a-b+c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'+'+c+'+'+d+'=7'
elif a-b+c-d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'+'+c+'-'+d+'=7'
elif a-b-c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'-'+c+'+'+d+'=7'
else:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'-'+c+'-'+d+'=7'
print(ans)

Buggy submission (verdict: Runtime Error):
import sys
input = sys.stdin.readline

a, b, c, d = input()
a = int(a);b = int(b);c = int(c);d = int(d)
if a+b+c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'+'+b+'+'+c+'+'+d+'=7'
elif a+b+c-d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'+'+b+'+'+c+'-'+d+'=7'
elif a+b-c-d == 7:
     a = str(a);b = str(b);c = str(c);d = str(d)
     ans = a+'+'+b+'-'+c+'-'+d+'=7'
elif a+b-c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'+'+b+'-'+c+'+'+d+'=7'
elif a-b+c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'+'+c+'+'+d+'=7'
elif a-b+c-d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'+'+c+'-'+d+'=7'
elif a-b-c+d == 7:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'-'+c+'+'+d+'=7'
else:
    a = str(a);b = str(b);c = str(c);d = str(d)
    ans = a+'-'+b+'-'+c+'-'+d+'=7'
print(ans)