#include <bits/stdc++.h>

using namespace std;

#define countof(a) (sizeof(a)/sizeof(*a))

#define vi vector<int>
#define vvi vector<vector<int> >
#define vpi vector<pi >
#define pi pair<int,int>
#define fi first
#define se second
#define all(n) n.begin(), n.end()

#define FROMTO(var, from, to) for (register int var = (from), var##down = ((int)(to)) < ((int)(from));var##down ? (var >= (int)(to)) : (var <= (int)(to));var##down ? var-- : var++)
#define FOR(var, to)          FROMTO(var, 0, (to)-1)
#define DOWN(var, from)       FROMTO(var, (from)-1, 0) 

#define INIT(var, val) FOR(i,countof(var)) var[i] = val
#define INPUT(var) FOR(i,countof(var)) cin >> var[i]
#define INPUT1(var) FOR(i,countof(var)) cin >> var[i], var[i]--

#define SORT(v) qsort(v,countof(v),sizeof(*v),int_less)
#define SORTT(v) qsort(v,countof(v),sizeof(*v),int_greater)
#define QSORT(v,b) qsort(v,countof(v),sizeof(*v),b)

#define MOD 1000000007
#define INF ((1 << 30)-1)
#define LINF ((1LL << 62)-1)

typedef uint8_t u8;
typedef uint16_t u16;
typedef uint32_t u32;
typedef uint64_t u64;
typedef int8_t s8;
typedef int16_t s16;
typedef int32_t s32;
typedef int64_t s64;

template<int mod>
struct ModInt{
    int x;
    ModInt():x(0){}
    ModInt(long long y):x(y>=0?y%mod:(mod-(-y)%mod)%mod){}
    ModInt &operator+=(const ModInt &p){
        if((x+=p.x)>=mod)x-=mod;
        return *this;
    }
    ModInt &operator-=(const ModInt &p){
        if((x+=mod-p.x)>=mod)x-=mod;
        return *this;
    }
    ModInt &operator*=(const ModInt &p){
        x=(int)(1LL*x*p.x%mod);
        return *this;
    }
    ModInt &operator/=(const ModInt &p){
        *this*=p.inverse();
        return *this;
    }
    ModInt operator-()const{return ModInt(-x);}
    ModInt operator+(const ModInt &p)const{return ModInt(*this)+=p;}
    ModInt operator-(const ModInt &p)const{return ModInt(*this)-=p;}
    ModInt operator*(const ModInt &p)const{return ModInt(*this)*=p;}
    ModInt operator/(const ModInt &p)const{return ModInt(*this)/=p;}
    bool operator==(const ModInt &p)const{return x==p.x;}
    bool operator!=(const ModInt &p)const{return x!=p.x;}
    operator int() const { return x; }
    ModInt operator=(const int p) {x = p; return ModInt(*this);}
    ModInt inverse()const{
        int a=x,b=mod,u=1,v=0,t;
        while(b>0){
            t=a/b;
            a-=t*b;
            swap(a,b);
            u-=t*v;
            swap(u,v);
        }
        return ModInt(u);
    }
    friend ostream &operator<<(ostream &os,const ModInt<mod> &p){
        return os<<p.x;
    }
    friend istream &operator>>(istream &is,ModInt<mod> &a){
        long long x;
        is>>x;
        a=ModInt<mod>(x);
        return (is);
    }
};
typedef ModInt<MOD> mint;

struct UnionFind{
    vi data;
    UnionFind(int size):data(size,-1){}
    bool unite(int x,int y) {
        x=root(x);y=root(y);
        if(x!=y){
            if(data[y]<data[x])swap(x,y);
            data[x]+=data[y];data[y]=x;
        }
        return x!=y;
    }
    bool find(int x,int y) {
        return root(x)==root(y);
    }
    int root(int x) {
        return data[x]<0?x:data[x]=root(data[x]);
    }
    int size(int x) {
        return -data[root(x)];
    }
    bool united() {
        int comroot = -1;
        FOR(i,data.size()) {
            if (comroot != -1 && root(i) != comroot) return false;
            comroot = root(i);
        }
        return true;
    }
};

template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
set<Key> operator+(set<Key>& a, set<Key>& b) {
    set<Key> c = a;
    for (auto i : b) 
        c.insert(i);
    return c;
} 
template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
set<Key> operator+=(set<Key>& a, set<Key>& b) {
    for (auto& i : b)
        a.insert(i);
    return a;
}

template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
set<Key> operator*(set<Key>& a, set<Key>& b) {
    set<Key> c;
    for (auto& i : a)
        if (b.count(i)) c.insert(i);
    return c;
}
template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
set<Key> operator*=(set<Key>& a, set<Key>& b) {
    set<Key> c;
    for (auto& i : a)
        if (b.count(i)) c.insert(i);
        
    return a = c;
}

template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
set<Key> operator-(set<Key>& a, set<Key>& b) {
    set<Key> c;
    for (auto& i : a)
        if (!b.count(i)) c.insert(i);
        
    return c;
}
template<class Key, class Compare = less<Key>, class Allocator = allocator<Key>>
set<Key> operator-=(set<Key>& a, set<Key>& b) {
    set<Key> c;
    for (auto& i : a)
        if (!b.count(i)) c.insert(i);
        
    return a = c;
}

static inline int ri() {
  int a;
  scanf("%d", &a);
  return a;
}

int mpow(int num, int times) {
    mint next = num;
  mint res = 1;
  while (num) {
    if (num%2)
            res *= next;
    next *= next;
    num /= 2;
  }
  return res.x;
}

int int_less(const void *a, const void *b) {
  return (*((const int*)a) - *((const int*)b));
}
int int_greater(const void *a, const void *b) {
  return (*((const int*)b) - *((const int*)a));
}

int main() {
    int n = ri();
    int m = ri();
    int x[m];
    int y[m];
    FOR(i,m) x[i]=ri()-1,y[i]=ri()-1;
    bool possible[n];
    INIT(possible,0);
    possible[0]=true;
    int num[n];
    INIT(num,1);
    FOR(i,m) {
      num[x[i]]--;
      num[y[i]]++;
      if (possible[x[i]])
        possible[y[i]]=true;
      if (!num[x[i]])
        possible[x[i]]=false;
    }
    
    int res = 0;
    FOR(i,n) res += possible[i];
    cout << res << endl;
    return 0;
}

Measured memory_bytes: 1536