`Do[threetest =
MatrixRank[{{threepoints[[i]][[2]][[1]] -
threepoints[[i]][[1]][[1]],
threepoints[[i]][[2]][[2]] - threepoints[[i]][[1]][[2]]},
{threepoints[[i]][[3]][[1]] - threepoints[[i]][[1]][[1]],
threepoints[[i]][[3]][[2]] - threepoints[[i]][[1]][[2]]}}];
If[threetest < 2, Break[], 1], {i, Binomial[n, 3]}]`