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Python

#!/usr/bin/env python3
"""Project Euler Problem 2: Find sum of even Fibonacci numbers below 4,000,000."""
def sum_even_fibs(limit: int) -> int:
"""Return sum of even Fibonacci numbers less than limit."""
a, b = 1, 2
total = 0
while b < limit:
if b % 2 == 0:
total += b
a, b = b, a + b
return total
if __name__ == "__main__":
limit = 4_000_000
result = sum_even_fibs(limit)
print(f"Sum of even Fibonacci numbers below {limit}: {result}")
# Verification assertion
expected = 4613732
assert result == expected, f"Expected {expected}, got {result}"
print(f"VERIFIED: result matches expected value {expected}")