class SegTree:
    def __init__(self, op, e, v):
        n = len(v)
        log = 0
        while (1 << log) < n:
            log += 1
        size = 1 << log
        
        d = [e] * (2 * size)
        
        for i in range(n):
            d[size + i] = v[i]
            
        self._op = op
        self._e = e
        self._n = n
        self._log = log
        self._size = size
        self._d = d
        
        for i in range(self._size - 1, 0, -1):
            self._update(i)

    def _update(self, k):
        self._d[k] = self._op(self._d[2 * k], self._d[2 * k + 1])

    def set(self, p, x):
        p += self._size
        self._d[p] = x
        for i in range(1, self._log + 1):
            self._update(p >> i)

    def get(self, p):
        return self._d[p + self._size]

    def prod(self, l, r):
        sml = self._e
        smr = self._e
        l += self._size
        r += self._size
        while l < r:
            if l & 1:
                sml = self._op(sml, self._d[l])
                l += 1
            if r & 1:
                r -= 1
                smr = self._op(self._d[r], smr)
            l >>= 1
            r >>= 1
        return self._op(sml, smr)

    def all_prod(self):
        return self._d[1]