import std.stdio, std.conv, std.math, std.string, std.range, std.array,
       std.algorithm;

void main(){
  readln();
  auto t = readln().strip().split().map!(to!int)().array().sort().uniq().array();
  auto u = t.dup[1..$];
  auto v = t[0..$-1];
  if(u.empty) {
    writeln("0");
    return;
  }
  u[] -= v[];
  u.reduce!min().writeln();
}