#include <stdio.h>

int main()
{
    int n;
    scanf("%d", &n);
    int i = 1, ans = 0, delta = 1, cnt = 0;
    while (i <= n)
    {
        ans++;
        cnt++;
        if (cnt == 2)
            delta++, cnt = 0;
        i += delta;
    }
    printf("%d\n", ans);
}