FrogRiverOne

Python

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(X, A):
    # write your code in Python 3.6
    position = set()

    for i, a in enumerate(A):
        if a <= X:
            position.add(a)
        if len(position) >= X:
            return i
    return -1