Buggy python submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-
import bisect
import heapq
import math
import random
from collections import Counter, defaultdict, deque
from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal
from fractions import Fraction
from functools import lru_cache, reduce
from itertools import combinations, combinations_with_replacement, product, permutations, accumulate
from operator import add, mul, sub, itemgetter, attrgetter


import sys
# sys.setrecursionlimit(10**6)
# readline = sys.stdin.buffer.readline
readline = sys.stdin.readline

INF = 2**62-1


def read_int():
    return int(readline())


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


def read_float():
    return float(readline())


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


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


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


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


def mt(f):
    import time

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

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

    return wrap


@mt
def slv(N, W, WV):
    vl = {}
    vl[WV[0][0]] = list()
    vl[WV[0][0]+1] = list()
    vl[WV[0][0]+2] = list()
    vl[WV[0][0]+3] = list()
    for w, v in WV:
        vl[w].append(v)

    for v in vl.values():
        v.sort(reverse=True)
        v.insert(0, 0)

    wl = vl.keys()
    wi, wj, wk = wl
    ans = 0
    vis = 0
    for i, vi in enumerate(vl[wi]):
        if wi * i > W:
            break
        vis += vi
        vjs = 0
        for j, vj in enumerate(vl[wj]):
            if wi * i + wj * j > W:
                break
            vjs += vj
            vks = 0
            for k, vk in enumerate(vl[wk]):
                if wi*i + wj*j + wk*k> W:
                    break
                vks += vk
                ans = max(ans, vis+vjs+vks)
    return ans





def main():
    N, W = read_int_n()
    WV = [read_int_n() for _ in range(N)]
    print(slv(N, W, WV))


if __name__ == '__main__':
    main()


Fixed submission:
# -*- coding: utf-8 -*-
import bisect
import heapq
import math
import random
from collections import Counter, defaultdict, deque
from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal
from fractions import Fraction
from functools import lru_cache, reduce
from itertools import combinations, combinations_with_replacement, product, permutations, accumulate
from operator import add, mul, sub, itemgetter, attrgetter


import sys
# sys.setrecursionlimit(10**6)
# readline = sys.stdin.buffer.readline
readline = sys.stdin.readline

INF = 2**62-1


def read_int():
    return int(readline())


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


def read_float():
    return float(readline())


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


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


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


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


def mt(f):
    import time

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

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

    return wrap


@mt
def slv(N, W, WV):
    vl = {}
    vl[WV[0][0]] = list()
    vl[WV[0][0]+1] = list()
    vl[WV[0][0]+2] = list()
    vl[WV[0][0]+3] = list()
    for w, v in WV:
        vl[w].append(v)

    for v in vl.values():
        v.sort(reverse=True)
        v.insert(0, 0)


    wi, wj, wk, wl = vl.keys()
    ans = 0
    vis = 0
    for i, vi in enumerate(vl[wi]):
        if wi * i > W:
            break
        vis += vi
        vjs = 0
        for j, vj in enumerate(vl[wj]):
            if wi * i + wj * j > W:
                break
            vjs += vj
            vks = 0
            for k, vk in enumerate(vl[wk]):
                if wi*i + wj*j + wk*k> W:
                    break
                vks += vk
                vls = 0
                for l, vll in enumerate(vl[wl]):
                    if wi*i + wj*j + wk*k + wl*l> W:
                        break
                    vls += vll
                ans = max(ans, vis+vjs+vks+vls)
    return ans





def main():
    N, W = read_int_n()
    WV = [read_int_n() for _ in range(N)]
    print(slv(N, W, WV))


if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-
import bisect
import heapq
import math
import random
from collections import Counter, defaultdict, deque
from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal
from fractions import Fraction
from functools import lru_cache, reduce
from itertools import combinations, combinations_with_replacement, product, permutations, accumulate
from operator import add, mul, sub, itemgetter, attrgetter


import sys
# sys.setrecursionlimit(10**6)
# readline = sys.stdin.buffer.readline
readline = sys.stdin.readline

INF = 2**62-1


def read_int():
    return int(readline())


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


def read_float():
    return float(readline())


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


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


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


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


def mt(f):
    import time

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

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

    return wrap


@mt
def slv(N, W, WV):
    vl = {}
    vl[WV[0][0]] = list()
    vl[WV[0][0]+1] = list()
    vl[WV[0][0]+2] = list()
    for w, v in WV:
        vl[w].append(v)

    for v in vl.values():
        v.sort(reverse=True)
        v.insert(0, 0)
    wl = vl.keys()
    wi, wj, wk = wl
    ans = 0
    vis = 0
    for i, vi in enumerate(vl[wi]):
        if wi * i > W:
            break
        vis += vi
        vjs = 0
        for j, vj in enumerate(vl[wj]):
            if wi * i + wj * j > W:
                break
            vjs += vj
            vks = 0
            for k, vk in enumerate(vl[wk]):
                if wi*i + wj*j + wk*k> W:
                    break
                vks += vk
                ans = max(ans, vis+vjs+vks)
    return ans





def main():
    N, W = read_int_n()
    WV = [read_int_n() for _ in range(N)]
    print(slv(N, W, WV))


if __name__ == '__main__':
    main()


Fixed submission:
# -*- coding: utf-8 -*-
import bisect
import heapq
import math
import random
from collections import Counter, defaultdict, deque
from decimal import ROUND_CEILING, ROUND_HALF_UP, Decimal
from fractions import Fraction
from functools import lru_cache, reduce
from itertools import combinations, combinations_with_replacement, product, permutations, accumulate
from operator import add, mul, sub, itemgetter, attrgetter


import sys
# sys.setrecursionlimit(10**6)
# readline = sys.stdin.buffer.readline
readline = sys.stdin.readline

INF = 2**62-1


def read_int():
    return int(readline())


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


def read_float():
    return float(readline())


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


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


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


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


def mt(f):
    import time

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

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

    return wrap


@mt
def slv(N, W, WV):
    vl = {}
    vl[WV[0][0]] = list()
    vl[WV[0][0]+1] = list()
    vl[WV[0][0]+2] = list()
    vl[WV[0][0]+3] = list()
    for w, v in WV:
        vl[w].append(v)

    for v in vl.values():
        v.sort(reverse=True)
        v.insert(0, 0)


    wi, wj, wk, wl = vl.keys()
    ans = 0
    vis = 0
    for i, vi in enumerate(vl[wi]):
        if wi * i > W:
            break
        vis += vi
        vjs = 0
        for j, vj in enumerate(vl[wj]):
            if wi * i + wj * j > W:
                break
            vjs += vj
            vks = 0
            for k, vk in enumerate(vl[wk]):
                if wi*i + wj*j + wk*k> W:
                    break
                vks += vk
                vls = 0
                for l, vll in enumerate(vl[wl]):
                    if wi*i + wj*j + wk*k + wl*l> W:
                        break
                    vls += vll
                ans = max(ans, vis+vjs+vks+vls)
    return ans





def main():
    N, W = read_int_n()
    WV = [read_int_n() for _ in range(N)]
    print(slv(N, W, WV))


if __name__ == '__main__':
    main()