import std.conv;
import std.stdio;
import std.string;
void main() {
int n = readln.strip.to!int;
string s = readln.strip;
foreach (from; 0 .. n)
foreach (jump; 1 .. n) {
bool ok;
foreach (i; 0 .. 5) {
int pos = from + i * jump;
if (pos >= n || s[pos] != '*') {
ok = true;
break;
}
}
if (!ok)
return writeln("yes");
}
writeln("no");
}
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