Buggy python submission (verdict: Runtime Error):
def 解():
    sS = input().rstrip()
    dsS = set()
    for s in sS:
        if s not in dsS:
            dsS.add(s)
    iK = int(input())
    iL = len(sS)
    iC = 0
    for s in sorted(list(dsS)):
        sDic = set()
        indexes = []
        for i in range(iL):
            if sS[i] == s:
                indexes.append(i)
        if iK < iL // len(indexes) + 1:
            for i in indexes:
                for j in range(1,iK+1):
                    if i+j <= iL:
                        sDic.add(sS[i:i+j])
            aS = sorted(list(sDic))
            print(aS[iK -1])
            exit()
        for i in indexes:
            for j in range(1,iL -i+1):
                sDic.add(sS[i:i+j])
        aS = sorted(list(sDic))
        iLS = len(aS)
        if iC + iLS < iK:
            iC += iLS
            continue
        else:
            print(aS[iK -iC-1])
            exit()
解()



Fixed submission:
def 解():
    sS = input().rstrip()
    dsS = set()
    for s in sS:
        if s not in dsS:
            dsS.add(s)
    iK = int(input())
    iL = len(sS)
    iC = 0
    for s in sorted(list(dsS)):
        sDic = set()
        indexes = []
        for i in range(iL):
            if sS[i] == s :
                if i != 0 and i != iL-1:
                    if sS[i-1] != s or sS[i+1] != s:
                        indexes.append(i)
                else:
                    indexes.append(i)
        if iK < iL :
            for i in indexes:
                for j in range(1,iK+1):
                    if i+j <= iL:
                        sDic.add(sS[i:i+j])
            aS = sorted(list(sDic))
            if iK <= len(aS) :
                print(aS[iK - iC -1])
                exit()
            else:
                iC += len(aS)
        else:
            for i in indexes:
                for j in range(1,iL -i+1):
                    sDic.add(sS[i:i+j])
            aS = sorted(list(sDic))
            iLS = len(aS)
            if iC + iLS < iK:
                iC += iLS
                continue
            else:
                print(aS[iK -iC-1])
                exit()
解()

Buggy python submission (verdict: Runtime Error):
def 解():
    sS = input().rstrip()
    dsS = set()
    for s in sS:
        if s not in dsS:
            dsS.add(s)
    iK = int(input())
    iL = len(sS)
    iC = 0
    for s in sorted(list(dsS)):
        sDic = set()
        indexes = []
        for i in range(iL):
            if sS[i] == s:
                indexes.append(i)
        if iK < iL // len(indexes):
            for i in indexes:
                for j in range(1,iK+1):
                    sDic.add(sS[i:i+j])
            aS = sorted(list(sDic))
            print(aS[iK -1])
            exit()
        for i in indexes:
            for j in range(1,iL -i+1):
                sDic.add(sS[i:i+j])
        aS = sorted(list(sDic))
        iLS = len(aS)
        if iC + iLS < iK:
            iC += iLS
            continue
        else:
            print(aS[iK -iC-1])
            exit()
解()


Fixed submission:
def 解():
    sS = input().rstrip()
    dsS = set()
    for s in sS:
        if s not in dsS:
            dsS.add(s)
    iK = int(input())
    iL = len(sS)
    iC = 0
    for s in sorted(list(dsS)):
        sDic = set()
        indexes = []
        for i in range(iL):
            if sS[i] == s :
                if i != 0 and i != iL-1:
                    if sS[i-1] != s or sS[i+1] != s:
                        indexes.append(i)
                else:
                    indexes.append(i)
        if iK < iL :
            for i in indexes:
                for j in range(1,iK+1):
                    if i+j <= iL:
                        sDic.add(sS[i:i+j])
            aS = sorted(list(sDic))
            if iK <= len(aS) :
                print(aS[iK - iC -1])
                exit()
            else:
                iC += len(aS)
        else:
            for i in indexes:
                for j in range(1,iL -i+1):
                    sDic.add(sS[i:i+j])
            aS = sorted(list(sDic))
            iLS = len(aS)
            if iC + iLS < iK:
                iC += iLS
                continue
            else:
                print(aS[iK -iC-1])
                exit()
解()

Buggy python submission (verdict: Time Limit Exceeded):
def 解():
    sS = input().rstrip()
    dsS = set()
    for s in sS:
        if s not in dsS:
            dsS.add(s)
    iK = int(input())
    iL = len(sS)
    iC = 0
    for s in sorted(list(dsS)):
        sDic = set()
        indexes = []
        for i in range(iL):
            if sS[i] == s:
                indexes.append(i)
        for i in indexes:
            for j in range(1,iL -i+1):
                sDic.add(sS[i:i+j])
        aS = sorted(list(sDic))
        iLS = len(aS)
        if iC + iLS < iK:
            iC += iLS
            continue
        else:
            print(aS[iK -iC-1])
            exit()
解()


Fixed submission:
def 解():
    sS = input().rstrip()
    dsS = set()
    for s in sS:
        if s not in dsS:
            dsS.add(s)
    iK = int(input())
    iL = len(sS)
    iC = 0
    for s in sorted(list(dsS)):
        sDic = set()
        indexes = []
        for i in range(iL):
            if sS[i] == s :
                if i != 0 and i != iL-1:
                    if sS[i-1] != s or sS[i+1] != s:
                        indexes.append(i)
                else:
                    indexes.append(i)
        if iK < iL :
            for i in indexes:
                for j in range(1,iK+1):
                    if i+j <= iL:
                        sDic.add(sS[i:i+j])
            aS = sorted(list(sDic))
            if iK <= len(aS) :
                print(aS[iK - iC -1])
                exit()
            else:
                iC += len(aS)
        else:
            for i in indexes:
                for j in range(1,iL -i+1):
                    sDic.add(sS[i:i+j])
            aS = sorted(list(sDic))
            iLS = len(aS)
            if iC + iLS < iK:
                iC += iLS
                continue
            else:
                print(aS[iK -iC-1])
                exit()
解()

Buggy python submission (verdict: Time Limit Exceeded):
def 解():
    sS = input().rstrip()
    iK = int(input())
    iL = len(sS)
    iC = 0
    sAbc = "abcdefghijklmnopqrstuvwxyz"
    for s in sAbc:
        sDic = set()
        indexes = []
        for i in range(iL):
            if sS[i] == s:
                indexes.append(i)
        for i in indexes:
            for j in range(1,iL -i+1):
                sDic.add(sS[i:i+j])
        aS = sorted(list(sDic))
        iLS = len(aS)
        if iC + iLS < iK:
            iC += iLS
            continue
        else:
            print(aS[iK -iC-1])
            exit()
解()


Fixed submission:
def 解():
    sS = input().rstrip()
    dsS = set()
    for s in sS:
        if s not in dsS:
            dsS.add(s)
    iK = int(input())
    iL = len(sS)
    iC = 0
    for s in sorted(list(dsS)):
        sDic = set()
        indexes = []
        for i in range(iL):
            if sS[i] == s :
                if i != 0 and i != iL-1:
                    if sS[i-1] != s or sS[i+1] != s:
                        indexes.append(i)
                else:
                    indexes.append(i)
        if iK < iL :
            for i in indexes:
                for j in range(1,iK+1):
                    if i+j <= iL:
                        sDic.add(sS[i:i+j])
            aS = sorted(list(sDic))
            if iK <= len(aS) :
                print(aS[iK - iC -1])
                exit()
            else:
                iC += len(aS)
        else:
            for i in indexes:
                for j in range(1,iL -i+1):
                    sDic.add(sS[i:i+j])
            aS = sorted(list(sDic))
            iLS = len(aS)
            if iC + iLS < iK:
                iC += iLS
                continue
            else:
                print(aS[iK -iC-1])
                exit()
解()