N, Q = map(int, input().split())
S = input()

alpha =['a','b','c','d','e','f','g','h','i','j','k','l','m','n',
        'o','p','q','r','s','t','u','v','w','x','y','z']

data = [[[0] for k in range(26)] for _ in range(int(N*(N+1)/2))]

for i in range(N):
    for j in range(i,N):
        for k in range(26):
            c = S.count(alpha[k], i, j+1)
            data[int(N*i+j-i*(i+1)/2)][k] = c

for i in range(Q):
    l, r, x = list(map(int, input().split()))
    d = data[int(N*(l-1)+r-1-l*(l-1)/2)][0]
    for j in range(26):
        if d >= x:
            print(alpha[j])
            break
        d += data[int(N*(l-1)+r-1-l*(l-1)/2)][j+1]