import sys
sys.setrecursionlimit(1000000000)

#
# Solution Template for Tennis Robot II
# 
# Australian Informatics Olympiad 2024
# 
# This file is provided to assist with reading and writing of the input
# files for the problem. You may modify this file however you wish, or
# you may choose not to use this file at all.
#

# N is the number of bins.
N = 0

# M is the number of instructions.
M = 0

# X contains the number of balls in each bin. Note that this list starts from 1
# (not 0), and so the values are X[1] to X[N].
X = []

# A and B contain the instructions. Note that the lists start from 0, and so
# the instructions are (A[0], B[0]) to (A[M-1], B[M-1]).
A = []
B = []

# Open the input and output files.
input_file = open("tennisin.txt", "r")
output_file = open("tennisout.txt", "w")

# Read the values of N, M, X, A, and B from input file.
input_line = input_file.readline().strip()
N, M = map(int, input_line.split())

# Values in X are indexed from 1 to N (not 0 to N-1)
input_line = input_file.readline().strip()
X = [0] + list(map(int, input_line.split()))

for i in range(0, M):
    input_vars = list(map(int, input_file.readline().strip().split()))
    A.append(input_vars[0])
    B.append(input_vars[1])

# TODO: This is where you should compute your solution. Store the number of
# instructions that the robot will successfully complete (or -1 if it will run
# forever) into the variable answer.

answer = 0

# Write the answer to the output file.
if answer == -1:
    output_file.write("FOREVER\n")
else:
    output_file.write("%d\n" % (answer))

# Finally, close the input/output files.
input_file.close()
output_file.close()