/f warp error

[15:09:05 INFO]: player issued server command: /f warp gg
[15:09:05 ERROR]: null
org.bukkit.command.CommandException: Unhandled exception executing 'f warp gg' in com.massivecraft.mcore.cmd.MCoreBukkitCommand(CmdFactions)
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:200) ~[spigot.jar:git-Spigot-1223]
        at org.bukkit.craftbukkit.v1_7_R1.CraftServer.dispatchCommand(CraftServer.java:546) ~[spigot.jar:git-Spigot-1223]
        at net.minecraft.server.v1_7_R1.PlayerConnection.handleCommand(PlayerConnection.java:940) [spigot.jar:git-Spigot-1223]
        at net.minecraft.server.v1_7_R1.PlayerConnection.a(PlayerConnection.java:815) [spigot.jar:git-Spigot-1223]
        at net.minecraft.server.v1_7_R1.PacketPlayInChat.a(PacketPlayInChat.java:28) [spigot.jar:git-Spigot-1223]
        at net.minecraft.server.v1_7_R1.PacketPlayInChat.handle(PacketPlayInChat.java:65) [spigot.jar:git-Spigot-1223]
        at net.minecraft.server.v1_7_R1.NetworkManager.a(NetworkManager.java:147) [spigot.jar:git-Spigot-1223]
        at net.minecraft.server.v1_7_R1.ServerConnection.c(SourceFile:134) [spigot.jar:git-Spigot-1223]
        at net.minecraft.server.v1_7_R1.MinecraftServer.u(MinecraftServer.java:657) [spigot.jar:git-Spigot-1223]
        at net.minecraft.server.v1_7_R1.DedicatedServer.u(DedicatedServer.java:273) [spigot.jar:git-Spigot-1223]
        at net.minecraft.server.v1_7_R1.MinecraftServer.t(MinecraftServer.java:540) [spigot.jar:git-Spigot-1223]
        at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:446) [spigot.jar:git-Spigot-1223]
        at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617) [spigot.jar:git-Spigot-1223]
Caused by: java.lang.NoClassDefFoundError: net/ess3/api/IEssentials
        at markehme.factionsplus.EssentialsIntegration.handleTeleport(EssentialsIntegration.java:151) ~[?:?]
        at markehme.factionsplus.Cmds.CmdWarp.performfp(CmdWarp.java:321) ~[?:?]
        at markehme.factionsplus.Cmds.FPCommand.perform(FPCommand.java:20) ~[?:?]
        at com.massivecraft.mcore.cmd.MCommand.execute(MCommand.java:229) ~[?:?]
        at com.massivecraft.mcore.cmd.MCommand.execute(MCommand.java:221) ~[?:?]
        at com.massivecraft.mcore.cmd.MCommand.execute(MCommand.java:236) ~[?:?]
        at com.massivecraft.mcore.cmd.MCoreBukkitCommand.execute(MCoreBukkitCommand.java:85) ~[?:?]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:196) ~[spigot.jar:git-Spigot-1223]
        ... 12 more
Caused by: java.lang.ClassNotFoundException: net.ess3.api.IEssentials
        at java.net.URLClassLoader$1.run(URLClassLoader.java:366) ~[?:1.7.0_45]
        at java.net.URLClassLoader$1.run(URLClassLoader.java:355) ~[?:1.7.0_45]
        at java.security.AccessController.doPrivileged(Native Method) ~[?:1.7.0_45]
        at java.net.URLClassLoader.findClass(URLClassLoader.java:354) ~[?:1.7.0_45]
        at org.bukkit.plugin.java.PluginClassLoader.findClass0(PluginClassLoader.java:80) ~[spigot.jar:git-Spigot-1223]
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:53) ~[spigot.jar:git-Spigot-1223]
        at java.lang.ClassLoader.loadClass(ClassLoader.java:425) ~[?:1.7.0_45]
        at java.lang.ClassLoader.loadClass(ClassLoader.java:358) ~[?:1.7.0_45]
        at markehme.factionsplus.EssentialsIntegration.handleTeleport(EssentialsIntegration.java:151) ~[?:?]
        at markehme.factionsplus.Cmds.CmdWarp.performfp(CmdWarp.java:321) ~[?:?]
        at markehme.factionsplus.Cmds.FPCommand.perform(FPCommand.java:20) ~[?:?]
        at com.massivecraft.mcore.cmd.MCommand.execute(MCommand.java:229) ~[?:?]
        at com.massivecraft.mcore.cmd.MCommand.execute(MCommand.java:221) ~[?:?]
        at com.massivecraft.mcore.cmd.MCommand.execute(MCommand.java:236) ~[?:?]
        at com.massivecraft.mcore.cmd.MCoreBukkitCommand.execute(MCoreBukkitCommand.java:85) ~[?:?]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:196) ~[spigot.jar:git-Spigot-1223]