diff --git a/main.cpp b/main.cpp
index 08f31d1..b8684bd 100644
--- a/main.cpp
+++ b/main.cpp
@@ -35,7 +35,7 @@ struct Pedestrian {
   Vector2d curr_vel, next_vel;  // velocity
   Vector2d destination;  // $\vectorarrow{r}^0_\alpha$
   Vector2d desired_next_node; // $\vectorarrow{r}^k_\alpha$
-  Vector2d actual_next_node; // $\vectorarrow{r}^k_\alpha$
+  Vector2d actual_next_node; // $\vectorarrow{r}^k_\alpha$ should be the same as desired_next_node but with obstacles it changes
   Vector2d F_i;  // social force
   double desired_v0;  // $v_\alpha^0$ desired speed in m/s e.g. 1.34
   double actual_v0;
@@ -111,8 +111,48 @@ Vector2d get_actual_direction(Pedestrian p) {
 }
 
 
-void compute_repulsive_effects_from_pedestrians(Vector2d *F_i) {
+// $\vectorarrow{f}_{\alpha \beta}(\vectorarrow{r}_{\alpha \beta}) = -\gradient_{\vectorarrow{r}_{\alpha \beta}} V_{\alpha \beta}[b(\vectorarrow{r}_{\alpha \beta})]$
+void compute_repulsive_effects_from_pedestrians(Pedestrian* P[n_p], Pedestrian* p, double distance) {
+  double delta_t = 0.5;  // assuming 0.5 seconds steps
+  Vector2d F_i = Vector2d();
+  for (int i = 0; i < n_p; i++) {
+    // only consider close pedestrians
+    if ((P[i]->curr_pos - p->curr_pos).norm() < distance) {
+      //
+      // $2b = \sqrt{(\Arrowvert \vectorarrow{r}_{\alpha \beta} \Arrowvert + \Arrowvert \vectorarrow{r}_{\alpha \beta} - v_\beta \Delta t \vectorarrow{e}_\beta \Arrowvert)^2 - (v_\beta \Delta t)^2}$
+      //
+      // $\Arrowvert \vectorarrow{r}_{\alpha \beta} \Arrowvert$ 
+      Vector2d r_ab = p->curr_pos - P[i]->curr_pos;
+      double r_ab_norm = (p->curr_pos - P[i]->curr_pos).norm();
 
+      // $\Arrowvert \vectorarrow{r}_{\alpha \beta} - v_\beta \Delta t \vectorarrow{e}_\beta \Arrowvert$
+      Vector2d e_beta = get_actual_direction(*P[i]);
+      Vector2d r_ab_something = p->curr_pos - P[i]->curr_pos - (e_beta * (P[i]->actual_v0 * delta_t));
+      double r_ab_something_norm = (p->curr_pos - P[i]->curr_pos - (e_beta * (P[i]->actual_v0 * delta_t))).norm();
+
+      // $v_\beta \Delta t$
+      double v_beta_delta_t = P[i]->actual_v0 * delta_t;
+
+      double b = sqrt((r_ab_norm + r_ab_something_norm) * (r_ab_norm + r_ab_something_norm) - (v_beta_delta_t) * (v_beta_delta_t)) / 2;
+      
+      //
+      // $\vectorarrow{f}_{\alpha \beta}(\vectorarrow{r}_{\alpha \beta}) = \frac{V^0_{\alpha \beta}}{\sigma}e^{-b / \sigma} \grad_{\vectorarrow{r}_{\alpha \beta}}b$
+      //
+      // TODO: what is $V^0_{\alpha \beta}$
+      //
+      double v_null_alpha_beta = 0.0;
+      double sigma = 0.0;
+      double e = 2.718;
+      //
+      // $\grad_{\vectorarrow{r}_{\alpha \beta}} = \frac{(\Arrowvert \vectorarrow{r}_{\alpha \beta} \Arrowvert + \Arrowvert \vectorarrow{r}_{\alpha \beta} - v_\beta \Delta t \vectorarrow{e}_\beta \Arrowvert) (\frac{\vectorarrow{r}_{\alpha \beta}}{\Arrowvert \vectorarrow{r}_{\alpha \beta} \Arrowvert} + \frac{\vectorarrow{r}_{\alpha \beta} - v_\beta \Delta t \vectorarrow{e}_\beta}{\Arrowvert \vectorarrow{r}_{\alpha \beta} - v_\beta \Delta t \vectorarrow{e}_\beta \Arrowvert})}{4b}$
+      //
+      Vector2d delta_r_alpha_beta = ( ( (r_ab / r_ab_norm) + (r_ab_something / r_ab_something_norm) ) * (r_ab_norm + r_ab_something_norm) ) / (4 * b);
+
+      Vector2d f_alpha_beta_r_alpha_beta = delta_r_alpha_beta * ((v_null_alpha_beta / sigma) * (exp(-b / sigma)));
+      F_i += f_alpha_beta_r_alpha_beta;
+    }
+  }
+  p->F_i += F_i;
 }
 
 void compute_repulsive_effects_from_borders(Vector2d *F_i) {
@@ -190,12 +230,13 @@ int main() {
 
 
 
-
-      compute_repulsive_effects_from_pedestrians(F[i]);
-
+      // TODO: define appropriate distance
+      double distance = 0.0;
+      compute_repulsive_effects_from_pedestrians(&P, &p, distance);
 
 
 
+      
       compute_repulsive_effects_from_borders(F[i]);