Buggy python submission (verdict: Runtime Error):
from fractions import gcd

def main():
    def fmin(m):
        return X * m + D * m *(m - 1)//2
    def fmax(m):
        return X * m + D * m * (2 * N - m - 1) // 2
    N, X, D = map(int, input().split())
    if D == 0:
        if X == 0:
            print(1)
        else:
            print(N + 1)
        exit(0)
    if D < 0:
        X, D = -X, -D
    if X > 0:
        ans = 0
        g = gcd(X, D)
        loop = D // g
        for d in range(N + 1):
            if loop <= d:
                mmin = max(fmin(d), fmax(d - loop) + D)
            else:
                mmin = fmin(d)
            mmax = fmax(d)
            ans += (mmax - mmin) // D + 1
        print(ans)
    elif X == 0:
        print(fmax(N) // D + 1)
    else:
        if X + D*(N - 1) >= 0:
            print(N // 0)
        else:
            ans = 0
            g = gcd(-X, D)
            loop = D // g
            for d in range(N + 1):
                if loop <= d:
                    mmax = min(fmax(d), fmin(d - loop) - D)
                else:
                    mmax = fmax(d)
                mmin = fmin(d)
                ans += (mmax - mmin) // D + 1
            print(ans)


if __name__ == '__main__':
    main()


Fixed submission:
from fractions import gcd

def main():
    def fmin(m):
        return X * m + D * m *(m - 1)//2
    def fmax(m):
        return X * m + D * m * (2 * N - m - 1) // 2
    N, X, D = map(int, input().split())
    if D == 0:
        if X == 0:
            print(1)
        else:
            print(N + 1)
        exit(0)
    if D < 0:
        X, D = -X, -D
    if X > 0:
        ans = 0
        g = gcd(X, D)
        loop = D // g
        for d in range(N + 1):
            if loop <= d:
                mmin = max(fmin(d), fmax(d - loop) + D)
            else:
                mmin = fmin(d)
            mmax = fmax(d)
            ans += (mmax - mmin) // D + 1
        print(ans)
    elif X == 0:
        print(fmax(N) // D + 1)
    else:
        if X + D*(N - 1) >= 0:
            ans = 0
            g = gcd(-X, D)
            loop = D // g
            for d in range(N + 1):
                dmax = fmax(d)
                dmin = fmin(d)
                if d < loop:
                    ans += (dmax - dmin) // D + 1
                else:
                    pmax = fmax(d - loop)
                    pmin = fmin(d - loop)
                    if pmax < dmax and pmin <= dmin:
                        mmin = max(dmin, pmax + D)
                        ans += (dmax - mmin) // D + 1
                    elif pmax >= dmax and pmin > dmin:
                        mmax = min(dmax, pmin - D)
                        ans += (mmax - dmin) // D + 1
                    elif pmax < dmax and pmin > dmin:
                        ans += (dmax - pmax) // D + (pmin - dmin) // D
            print(ans)
                    
        else:
            ans = 0
            g = gcd(-X, D)
            loop = D // g
            for d in range(N + 1):
                if loop <= d:
                    mmax = min(fmax(d), fmin(d - loop) - D)
                else:
                    mmax = fmax(d)
                mmin = fmin(d)
                ans += (mmax - mmin) // D + 1
            print(ans)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
from fractions import gcd

def main():
    def fmin(m):
        return X * m + D * m *(m - 1)//2
    def fmax(m):
        return X * m + D * m * (2 * N - m - 1) // 2
    N, X, D = map(int, input().split())
    if D == 0:
        if X == 0:
            print(1)
        else:
            print(N + 1)
    if D < 0:
        X, D = -X, -D
    if X > 0:
        ans = 0
        g = gcd(X, D)
        loop = D // g
        for d in range(N + 1):
            if loop <= d:
                mmin = max(fmin(d), fmax(d - loop) + D)
            else:
                mmin = fmin(d)
            mmax = fmax(d)
            ans += (mmax - mmin) // D + 1
        print(ans)
    elif X == 0:
        print(fmax(N) // D + 1)
    else:
        ans = 0
        g = gcd(-X, D)
        loop = D // g
        for d in range(N + 1):
            if loop <= d:
                mmax = min(fmax(d), fmin(d - loop) - D)
            else:
                mmax = fmax(d)
            mmin = fmin(d)
            ans += (mmax - mmin) // D + 1
        print(ans)

if __name__ == '__main__':
    main()

Fixed submission:
from fractions import gcd

def main():
    def fmin(m):
        return X * m + D * m *(m - 1)//2
    def fmax(m):
        return X * m + D * m * (2 * N - m - 1) // 2
    N, X, D = map(int, input().split())
    if D == 0:
        if X == 0:
            print(1)
        else:
            print(N + 1)
        exit(0)
    if D < 0:
        X, D = -X, -D
    if X > 0:
        ans = 0
        g = gcd(X, D)
        loop = D // g
        for d in range(N + 1):
            if loop <= d:
                mmin = max(fmin(d), fmax(d - loop) + D)
            else:
                mmin = fmin(d)
            mmax = fmax(d)
            ans += (mmax - mmin) // D + 1
        print(ans)
    elif X == 0:
        print(fmax(N) // D + 1)
    else:
        if X + D*(N - 1) >= 0:
            ans = 0
            g = gcd(-X, D)
            loop = D // g
            for d in range(N + 1):
                dmax = fmax(d)
                dmin = fmin(d)
                if d < loop:
                    ans += (dmax - dmin) // D + 1
                else:
                    pmax = fmax(d - loop)
                    pmin = fmin(d - loop)
                    if pmax < dmax and pmin <= dmin:
                        mmin = max(dmin, pmax + D)
                        ans += (dmax - mmin) // D + 1
                    elif pmax >= dmax and pmin > dmin:
                        mmax = min(dmax, pmin - D)
                        ans += (mmax - dmin) // D + 1
                    elif pmax < dmax and pmin > dmin:
                        ans += (dmax - pmax) // D + (pmin - dmin) // D
            print(ans)
                    
        else:
            ans = 0
            g = gcd(-X, D)
            loop = D // g
            for d in range(N + 1):
                if loop <= d:
                    mmax = min(fmax(d), fmin(d - loop) - D)
                else:
                    mmax = fmax(d)
                mmin = fmin(d)
                ans += (mmax - mmin) // D + 1
            print(ans)


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
from fractions import gcd

def main():
    def fmin(m):
        return X * m + D * m *(m - 1)//2
    def fmax(m):
        return X * m + D * m * (2 * N - m - 1) // 2
    N, X, D = map(int, input().split())
    if D < 0:
        X, D = -X, -D
    if X > 0:
        ans = 0
        g = gcd(X, D)
        loop = D // g
        for d in range(N + 1):
            if loop <= d:
                mmin = max(fmin(d), fmax(d - loop) + D)
            else:
                mmin = fmin(d)
            mmax = fmax(d)
            ans += (mmax - mmin) // D + 1
        print(ans)
    elif X == 0:
        print(fmax(N) // D + 1)
    else:
        ans = 0
        g = gcd(-X, D)
        loop = D // g
        for d in range(N + 1):
            if loop <= d:
                mmax = min(fmax(d), fmin(d - loop) - D)
            else:
                mmax = fmax(d)
            mmin = fmin(d)
            ans += (mmax - mmin) // D + 1
        print(ans)

if __name__ == '__main__':
    main()

Fixed submission:
from fractions import gcd

def main():
    def fmin(m):
        return X * m + D * m *(m - 1)//2
    def fmax(m):
        return X * m + D * m * (2 * N - m - 1) // 2
    N, X, D = map(int, input().split())
    if D == 0:
        if X == 0:
            print(1)
        else:
            print(N + 1)
        exit(0)
    if D < 0:
        X, D = -X, -D
    if X > 0:
        ans = 0
        g = gcd(X, D)
        loop = D // g
        for d in range(N + 1):
            if loop <= d:
                mmin = max(fmin(d), fmax(d - loop) + D)
            else:
                mmin = fmin(d)
            mmax = fmax(d)
            ans += (mmax - mmin) // D + 1
        print(ans)
    elif X == 0:
        print(fmax(N) // D + 1)
    else:
        if X + D*(N - 1) >= 0:
            ans = 0
            g = gcd(-X, D)
            loop = D // g
            for d in range(N + 1):
                dmax = fmax(d)
                dmin = fmin(d)
                if d < loop:
                    ans += (dmax - dmin) // D + 1
                else:
                    pmax = fmax(d - loop)
                    pmin = fmin(d - loop)
                    if pmax < dmax and pmin <= dmin:
                        mmin = max(dmin, pmax + D)
                        ans += (dmax - mmin) // D + 1
                    elif pmax >= dmax and pmin > dmin:
                        mmax = min(dmax, pmin - D)
                        ans += (mmax - dmin) // D + 1
                    elif pmax < dmax and pmin > dmin:
                        ans += (dmax - pmax) // D + (pmin - dmin) // D
            print(ans)
                    
        else:
            ans = 0
            g = gcd(-X, D)
            loop = D // g
            for d in range(N + 1):
                if loop <= d:
                    mmax = min(fmax(d), fmin(d - loop) - D)
                else:
                    mmax = fmax(d)
                mmin = fmin(d)
                ans += (mmax - mmin) // D + 1
            print(ans)


if __name__ == '__main__':
    main()