#include <bits/stdc++.h>   using namespace std;   int ans = 1e9;   int f[1000010];   int main() {     int n, i, j;     scanf( %d , &n);     for (i = 2; i <= n; i++) {       if (!f[i]) {         for (j = 2 * i; j <= n; j += i) {           f[j] = i;         }       }       f[i] = i - f[i] + 1;     }     for (i = f[n]; i <= n; i++) {       if (f[i] < ans) ans = f[i];     }     cout << ans << endl;   }   