Problem p02782 (python)

Fixed submission:
# -*- coding: utf-8 -*-
import sys
# sys.setrecursionlimit(10**6)
# buff_readline = sys.stdin.buffer.readline
buff_readline = sys.stdin.readline
readline = sys.stdin.readline

INF = 2**62-1


def read_int():
    return int(buff_readline())


def read_int_n():
    return list(map(int, buff_readline().split()))


def read_float():
    return float(buff_readline())


def read_float_n():
    return list(map(float, buff_readline().split()))


def read_str():
    return readline().strip()


def read_str_n():
    return readline().strip().split()


def error_print(*args):
    print(*args, file=sys.stderr)


def mt(f):
    import time

    def wrap(*args, **kwargs):
        s = time.time()
        ret = f(*args, **kwargs)
        e = time.time()

        error_print(e - s, 'sec')
        return ret

    return wrap

class Combination:
    def __init__(self, n, mod):

        g1 = [1, 1]
        g2 = [1, 1]
        inverse = [0, 1]
        for i in range(2, n + 1):
            g1.append((g1[-1] * i) % mod)
            inverse.append((-inverse[mod % i] * (mod//i)) % mod)
            g2.append((g2[-1] * inverse[-1]) % mod)
        self.MOD = mod
        self.N = n
        self.g1 = g1
        self.g2 = g2
        self.inverse = inverse

    def __call__(self, n, r):
        if (r < 0 or r > n):
            return 0
        r = min(r, n-r)
        return self.g1[n] * self.g2[r] * self.g2[n-r] % self.MOD


class Mod:
    def __init__(self, m):
        self.m = m

    def add(self, a, b):
        return (a + b) % self.m

    def sub(self, a, b):
        return (a - b) % self.m

    def mul(self, a, b):
        return ((a % self.m) * (b % self.m)) % self.m

    def div(self, a, b):
        return self.mul(a, pow(b, self.m-2, self.m))

    def pow(self, a, b):
        return pow(a, b, self.m)


@mt
def slv(R1, C1, R2, C2):
    C = Combination(2*10**6+1, 10**9+7)
    M = Mod(10**9+7)
    ans = 0
    for r in range(R1, R2+1):
        a = C(C2+r+1, r+1)
        b = C(C1-1+r+1, r+1)
        ans = M.add(ans, M.sub(a, b))
    return ans



def main():
    R1, C1, R2, C2 = read_int_n()
    print(slv(R1, C1, R2, C2))


if __name__ == '__main__':
    main()

Buggy submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-
import sys
# sys.setrecursionlimit(10**6)
# buff_readline = sys.stdin.buffer.readline
buff_readline = sys.stdin.readline
readline = sys.stdin.readline

INF = 2**62-1


def read_int():
    return int(buff_readline())


def read_int_n():
    return list(map(int, buff_readline().split()))


def read_float():
    return float(buff_readline())


def read_float_n():
    return list(map(float, buff_readline().split()))


def read_str():
    return readline().strip()


def read_str_n():
    return readline().strip().split()


def error_print(*args):
    print(*args, file=sys.stderr)


def mt(f):
    import time

    def wrap(*args, **kwargs):
        s = time.time()
        ret = f(*args, **kwargs)
        e = time.time()

        error_print(e - s, 'sec')
        return ret

    return wrap

class Combination:
    def __init__(self, n, mod):

        g1 = [1, 1]
        g2 = [1, 1]
        inverse = [0, 1]
        for i in range(2, n + 1):
            g1.append((g1[-1] * i) % mod)
            inverse.append((-inverse[mod % i] * (mod//i)) % mod)
            g2.append((g2[-1] * inverse[-1]) % mod)
        self.MOD = mod
        self.N = n
        self.g1 = g1
        self.g2 = g2
        self.inverse = inverse

    def __call__(self, n, r):
        if (r < 0 or r > n):
            return 0
        r = min(r, n-r)
        return self.g1[n] * self.g2[r] * self.g2[n-r] % self.MOD


class Mod:
    def __init__(self, m):
        self.m = m

    def add(self, a, b):
        return (a + b) % self.m

    def sub(self, a, b):
        return (a - b) % self.m

    def mul(self, a, b):
        return ((a % self.m) * (b % self.m)) % self.m

    def div(self, a, b):
        return self.mul(a, pow(b, self.m-2, self.m))

    def pow(self, a, b):
        return pow(a, b, self.m)


@mt
def slv(R1, C1, R2, C2):
    C = Combination(2*10**6, 10**9+7)
    M = Mod(10**9+7)
    ans = 0
    for r in range(R1, R2+1):
        a = C(C2+r+1, r+1)
        b = C(C1-1+r+1, r+1)
        ans = M.add(ans, M.sub(a, b))
    return ans



def main():
    R1, C1, R2, C2 = read_int_n()
    print(slv(R1, C1, R2, C2))


if __name__ == '__main__':
    main()