#include<algorithm>
#include<iostream>
#include<iomanip>
#include<stdio.h>
#include<bitset>
#include<vector>
#include<string>
#include<queue>
#include<cmath>
#include<ctime>
#include<stack>
#include<map>
#include<set>
using namespace std;
typedef long long LL;
typedef long double LD;
typedef vector<LL> BIG;
typedef vector<int> VI;
typedef pair<LL,LL> PLL;
typedef pair<int,int> PII;
#define PRINT(a) cerr<<#a<<" = "<<(a)<<'\n'
#define B_E(a) a.begin(), a.end()
#define PB push_back
#define MP make_pair
#define S second
#define F first
inline void file() {
    #ifdef _WIN32
        srand(time(NULL));
        return;
    #endif

    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    if (0) {
        freopen(".in",  "r", stdin);
        freopen(".out", "w", stdout);
    }
}
inline void read(int& n) {
    #define nxt h = getchar_unlocked()
    #define nxt h = getchar()
    char h; n = 0;
    for (nxt; h<'0' || h>'9'; nxt);
    for (; h>='0' && h<='9'; nxt)
        n = n*10 + h-'0';
    #undef nxt
}




const clock_t MAXT = (100*CLOCKS_PER_SEC)/1000;
const int   PX[8] = {0,0,1,-1,1,1,-1,-1},
            PY[8] = {-1,1,0,0,-1,1,1,-1},
            N = 1e5 + 10,
            INF = 1e9,
            LENB = 1,
            MOD = 1e9 + 7;
const LL    INFL = 1e18,
            BASE = 10,
            MODL = 1e9 + 7;
const LD    EPS = 1e-6;

inline int rnd(int l = 0, int r = INF) {
    unsigned ans = 0;
    ans = (ans<<15) | rand();
    ans = (ans<<15) | rand();
    ans = (ans<<15) | rand();
    ans = (ans<<15) | rand();
    ans = (ans<<15) | rand();
    ans %= r-l+1;
    ans += l;
    return ans;
}

BIG a,b,x,y;


inline void write(BIG a) {
    int pos = a.size() - 1;
    while ( !a[pos] && pos )
        --pos;

    while ( pos >= 0 )
        cout<<a[pos--]%BASE;
}

inline BIG mult(BIG a, LL b) {
    BIG c;
    c.PB( a[0]*b );
    for (int i=1; i<a.size(); ++i) {
        c.PB( a[i]*b + c[i-1]/BASE );
        c[i-1] %= BASE;
    }

    while ( c.back() >= BASE ) {
        LL x = c.back()/BASE;
        c.back() %= BASE;
        if (x) c.PB(x);
    }
    return c;
}

inline void read_long(BIG& a) {
    #define nxt h = getchar_unlocked()
    #define nxt h = getchar()

    a.clear();
    char h;
    for (nxt; h<'0' || h>'9'; nxt);
    for (; h>='0' && h<='9'; nxt)
        a.PB(h-'0');
    reverse( B_E(a) );

    #undef nxt
}



inline BIG mult_long(BIG a, BIG b) {
    int n = a.size()+b.size()+10;
    BIG c(n);
    for (int i=0; i<n; ++i)
        c[i] = 0;

    for (int i=0; i<a.size(); ++i) {
        LL x = 0;
        for (int j=0; j<b.size() || x; ++j) {
            LL s = c[i+j] + x;
            if ( j < b.size() )
                s += a[i] * b[j];
            c[i+j] = s % BASE;
            x = s / BASE;
        }
    }

    while ( !c.empty() && !c.back() )
        c.pop_back();

    return c;
}

inline BIG sum(BIG a, BIG b) {
    BIG c;
    int mx,mn;
    mx = max(a.size(),b.size());
    mn = min(a.size(),b.size());


    c.PB( a[0]+b[0] );
    for (int i=1; i<mx+1; ++i) {
        c.PB( c[i-1]/BASE );

        if ( a.size() > i )
            c.back() += a[i];
        if ( b.size() > i )
            c.back() += b[i];
    }

    for (LL& i:c)
        i %= BASE;

    return c;
}





inline LL short_mod(BIG& a, LL b) {
    LL ans = 0;
    for (int i=a.size()-1; i>=0; --i)
        ans = (ans*10 + a[i]) % b;
    return ans;
}


inline BIG short_div(BIG& a, LL b) {
    BIG c;
    LL s = 0;
    for (int i=a.size()-1; i>=0; --i) {
        s = s*10 + a[i];

        if ( s>=b || !c.empty() )
            c.PB(s/b);
        s %= b;

    }

    if ( c.empty() )
        c.PB(0);
    reverse(B_E(c));
    return c;

}

inline BIG subtr(BIG a, BIG b) {
    int n = a.size();
    while ( !b.empty() && !b.back() )
        b.pop_back();

    while ( b.size() < n )
        b.PB(0);

    for (LL& i:b)
        i = BASE - 1 - i;
    b[0]++;

    a = sum(a,b);
    a.pop_back();
    while ( !a.empty() && !a.back() )
        a.pop_back();
    if ( a.empty() )
        a.PB(0);

    return a;
}


inline int cmp(BIG a, BIG b) {
    while ( !a.empty() && !a.back() ) a.pop_back();
    while ( !b.empty() && !b.back() ) b.pop_back();

    if ( a.size() > b.size() )
        return +1;

    if ( a.size() < b.size() )
        return -1;


    int n = a.size();
    for (int i=n-1; i>=0; --i) {
        if ( a[i]>b[i] ) return +1;
        if ( a[i]<b[i] ) return -1;
    }

    return 0;
}


inline void long_div(BIG a, BIG b, BIG& x, BIG& y) {
    x.clear();
    y.clear();
    y.PB(0);
    int cnt;
    BIG s;

    for (int i=a.size()-1; i>=0; --i) {
        y = mult(y,10);
        s.clear();
        s.PB(a[i]);
        y = sum(y,s);

        for (cnt=0; cmp(y,b) >= 0; ++cnt)
            y = subtr(y,b);

        x.PB(cnt);
    }

    reverse(B_E(x));
    while ( !x.empty() && !x.back() )
        x.pop_back();
}

inline BIG sqr(BIG a) {
    return mult_long(a,a);
}

inline BIG long_sqrt(BIG a) {
    BIG s; s.PB(1);
    while ( cmp(a, mult(sqr(s),100) ) != -1 )
        s = mult(s,10);

    for (int i=s.size()-1; i>=0; --i) {
        while ( cmp(a, sqr(s) ) != -1 )
            ++s[i];
        --s[i];
    }


    return s;
}


int main()
{ file();

    read_long(a);
    write( long_sqrt(a) );
















}