import std.conv, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.container, std.math, std.range, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken().to!int; }
long readLong() { return readToken().to!long; }
real readReal() { return readToken().to!real; }

void chmin(T)(ref T t, in T f) { if (t > f) t = f; }
void chmax(T)(ref T t, in T f) { if (t < f) t = f; }

int binarySearch(T)(in T[] as, in bool delegate(T) test) { int low = -1, upp = cast(int)(as.length); for (; low + 1 < upp; ) { int mid = (low + upp) >> 1; (test(as[mid]) ? low : upp) = mid; } return upp; }
int lowerBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a < val)); }
int upperBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a <= val)); }

/*
01
02

01 02
03

01 02 03
04 05 06
07

01 02 03 04
05

01 02 03 04 05
06 07
11

01 02 03 04 05 06
07

01 02 03 04 05 06 07
08 09 10 11
15 16 17
22 23
29

01 02 03 04 05 06 07 08
09 10 11 12 13 14 15 16
17 18 19 20 21 22 23 24
25 26 27 28 29
*/

immutable LIM = 100;
bool[] isnp;

void prepare() {
  isnp = new bool[LIM];
  isnp[0] = isnp[1] = true;
  foreach (i; 2 .. LIM) {
    if (!isnp[i]) {
      for (int j = i * i; j < LIM; j += i) {
        isnp[j] = true;
      }
    }
  }
}

int solveSmall(int N) {
  foreach (W; 1 .. N) {
    const H = (N + W + 1) / W;
    auto A = new bool[][](H, W);
    foreach (x; 0 .. H) foreach (y; 0 .. W) {
      A[x][y] = isnp[1 + x * W + y];
    }
    auto vis = new bool[][](H, W);
    void dfs(int x, int y) {
      vis[x][y] = true;
      foreach (dir; 0 .. 4) {
        const xx = x + [+1, 0, -1, 0][dir];
        const yy = y + [0, +1, 0, -1][dir];
        if (0 <= xx && xx < H && 0 <= yy && yy < W && A[x][y]) {
          if (!vis[xx][yy]) {
            dfs(xx, yy);
          }
        }
      }
    }
    dfs(0, 0);
    if (vis[(N - 1) / W][(N - 1) % W]) {
      return W;
    }
  }
  return -1;
}

void main() {
  prepare();
  
  try {
    for (; ; ) {
      const N = readToken();
      int ans;
      if (N.length <= 2) {
        ans = solveSmall(N.to!int);
      } else {
        ans = 8;
      }
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}