public Action:OnPlayerRunCmd(iClient, &buttons, &impulse, Float:vel[3], Float:angles[3], &weapon)
{
if (IsPlayerAlive(iClient))
{
static g_fLastButtons[MAXPLAYERS+1], g_fLastFlags[MAXPLAYERS+1], g_iJumps[MAXPLAYERS+1], fCurFlags, fCurButtons;
fCurFlags = GetEntityFlags(iClient);  
fCurButtons = GetClientButtons(iClient);  
if (g_fLastFlags[iClient] & FL_ONGROUND && !(fCurFlags & FL_ONGROUND) && !(g_fLastButtons[iClient] & IN_JUMP) && fCurButtons & IN_JUMP) g_iJumps[iClient]++;
else if(fCurFlags & FL_ONGROUND) g_iJumps[iClient] = 0;
else if(!(g_fLastButtons[iClient] & IN_JUMP) && fCurButtons & IN_JUMP && g_iJumps[iClient] == 1)
{  
g_iJumps[iClient]++;  
decl Float:vVel[3];
GetEntPropVector(iClient, Prop_Data, "m_vecVelocity", vVel);
vVel[2] = 250.0;
TeleportEntity(iClient, NULL_VECTOR, NULL_VECTOR, vVel);
}

g_fLastFlags[iClient] = fCurFlags;  
g_fLastButtons[iClient] = fCurButtons;
}
return Plugin_Continue;
}