def suma_equilibrada(f):
'''
>>> suma_equilibrada([1, 1, 1, 1])
1
>>> suma_equilibrada([10, 10, 7, 3, 30])
3
>>> suma_equilibrada([10, 20])
-1
>>> suma_equilibrada([-3, 5, -2])
2
>>> suma_equilibrada([0])
0
>>> suma_equilibrada([])
-1
'''
sa = 0
sp =sum(f)
for i in range(len(f)):
sa += f[i]
sp -= f[i]
if sa == sp:
return i
return -1
if __name__ == "__main__":
import doctest
doctest.testmod(verbose=True)