let somme3 a = let n = vect_lenght a and mini=a.(0);
for i=0 to n-1 do 
	for j=i to n-1 do
	s <- a.(i);
		for k = i + 1 to j do s <- s + a.(k) done ;
		if s < mini then mini <- s;
	done;
done;
mini ;;