#pragma GCC optimize ("Ofast")
#include<bits/stdc++.h>
using namespace std;
void *wmem;
char memarr[96000000];
template<class S, class T> inline S min_L(S a,T b){
  return a<=b?a:b;
}
template<class S, class T> inline S max_L(S a,T b){
  return a>=b?a:b;
}
template<class T> inline void walloc1d(T **arr, int x, void **mem = &wmem){
  static int skip[16] = {0, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1};
  (*mem) = (void*)( ((char*)(*mem)) + skip[((unsigned long long)(*mem)) & 15] );
  (*arr)=(T*)(*mem);
  (*mem)=((*arr)+x);
}
inline void rd(int &x){
  int k;
  int m=0;
  x=0;
  for(;;){
    k = getchar_unlocked();
    if(k=='-'){
      m=1;
      break;
    }
    if('0'<=k&&k<='9'){
      x=k-'0';
      break;
    }
  }
  for(;;){
    k = getchar_unlocked();
    if(k<'0'||k>'9'){
      break;
    }
    x=x*10+k-'0';
  }
  if(m){
    x=-x;
  }
}
inline void wt_L(char a){
  putchar_unlocked(a);
}
inline void wt_L(int x){
  int s=0;
  int m=0;
  char f[10];
  if(x<0){
    m=1;
    x=-x;
  }
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  if(m){
    putchar_unlocked('-');
  }
  while(s--){
    putchar_unlocked(f[s]+'0');
  }
}
inline void wt_L(unsigned x){
  int s=0;
  char f[10];
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  while(s--){
    putchar_unlocked(f[s]+'0');
  }
}
inline void wt_L(long long x){
  int s=0;
  int m=0;
  char f[20];
  if(x<0){
    m=1;
    x=-x;
  }
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  if(m){
    putchar_unlocked('-');
  }
  while(s--){
    putchar_unlocked(f[s]+'0');
  }
}
inline void wt_L(unsigned long long x){
  int s=0;
  char f[21];
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  while(s--){
    putchar_unlocked(f[s]+'0');
  }
}
inline void wt_L(double x){
  printf("%.15f",x);
}
inline void wt_L(const char c[]){
  int i=0;
  for(i=0;c[i]!='\0';i++){
    putchar_unlocked(c[i]);
  }
}
inline void wt_L(string &x){
  int i=0;
  for(i=0;x[i]!='\0';i++){
    putchar_unlocked(x[i]);
  }
}
template<class T, class S> struct maxflow{
  int node;
  int st;
  int ed;
  int *es;
  int *emem;
  int **edge;
  int **rev;
  int *level;
  int *qq;
  T **flow;
  T eps;
  void malloc(int N){
    int i;
    es = (int*)std::malloc(N*sizeof(int));
    emem = (int*)std::malloc(N*sizeof(int));
    level = (int*)std::malloc(N*sizeof(int));
    qq = (int*)std::malloc(N*sizeof(int));
    edge = (int**)std::malloc(N*sizeof(int*));
    rev = (int**)std::malloc(N*sizeof(int*));
    flow = (T**)std::malloc(N*sizeof(T*));
    for(i=(0);i<(N);i++){
      emem[i] = 0;
      edge[i] = rev[i] = NULL;
      flow[i] = NULL;
    }
  }
  void walloc(int N, void**mem = &wmem){
    int i;
    walloc1d(&es, N, mem);
    walloc1d(&emem, N, mem);
    walloc1d(&level, N, mem);
    walloc1d(&qq, N, mem);
    walloc1d(&edge, N, mem);
    walloc1d(&rev, N, mem);
    walloc1d(&flow, N, mem);
    (*mem) = (flow + N);
  }
  void levelize(void){
    int i;
    int j;
    int k;
    int t;
    int q_st = 0;
    int q_ed = 1;
    for(i=(0);i<(node);i++){
      level[i] = -1;
    }
    level[st] = 0;
    qq[0] = st;
    while(q_st != q_ed){
      i = qq[q_st++];
      t = level[i] + 1;
      for(j=(0);j<(es[i]);j++){
        if(flow[i][j] > eps){
          k = edge[i][j];
          if(level[k]!=-1){
            continue;
          }
          level[k] = t;
          qq[q_ed++] = k;
          if(k==ed){
            return;
          }
        }
      }
    }
  }
  S pushflow(int i, S lim){
    int j;
    int k;
    int ji;
    S s;
    S t;
    S res = 0;
    if(i==ed){
      return lim;
    }
    for(j=(0);j<(es[i]);j++){
      if(flow[i][j] > eps){
        k = edge[i][j];
        if(level[k] != level[i]+1){
          continue;
        }
        s =min_L(lim, (S)flow[i][j]);
        t = pushflow(k, s);
        if(!t){
          continue;
        }
        res += t;
        lim -= t;
        ji = rev[i][j];
        flow[i][j] -= t;
        flow[k][ji] += t;
        if(!lim){
          break;
        }
      }
    }
    if(lim){
      level[i] = -1;
    }
    return res;
  }
  S solve(int st_, int ed_){
    S res = 0;
    st = st_;
    ed = ed_;
    for(;;){
      levelize();
      if(level[ed] == -1){
        break;
      }
      res += pushflow(st, numeric_limits<S>::max());
    }
    return res;
  }
  void init(int N){
    int i;
    node = N;
    for(i=(0);i<(N);i++){
      es[i] = 0;
    }
    eps = (T)1e-9;
  }
  void memoryExpand(int i, int sz){
    if(sz <= emem[i]){
      return;
    }
    sz =max_L(sz,max_L(3, emem[i]*2));
    emem[i]=sz;
    edge[i] = (int*)realloc(edge[i], sz*sizeof(int));
    rev[i] = (int*)realloc(rev[i], sz*sizeof(int));
    flow[i] = (T*)realloc(flow[i], sz*sizeof(T));
  }
  void addEdge(int n1, int n2, T f1, T f2 = 0){
    int s1 = es[n1]++;
    int s2 = es[n2]++;
    if(s1 >= emem[n1]){
      memoryExpand(n1, es[n1]);
    }
    if(s2 >= emem[n2]){
      memoryExpand(n2, es[n2]);
    }
    edge[n1][s1]=n2;
    edge[n2][s2]=n1;
    flow[n1][s1]=f1;
    flow[n2][s2]=f2;
    rev[n1][s1]=s2;
    rev[n2][s2]=s1;
  }
  void addEdgeAdv(int n1, int n2, T f1, T f2 = 0){
    int s1 = es[n1]++;
    int s2 = es[n2]++;
    edge[n1][s1]=n2;
    edge[n2][s2]=n1;
    flow[n1][s1]=f1;
    flow[n2][s2]=f2;
    rev[n1][s1]=s2;
    rev[n2][s2]=s1;
  }
  void setGraph(int N, int M, int n1[], int n2[], T f1[], T f2[]){
    int i;
    node = N;
    for(i=(0);i<(N);i++){
      es[i] = 0;
    }
    for(i=(0);i<(M);i++){
      es[n1[i]]++;
      es[n2[i]]++;
    }
    for(i=(0);i<(N);i++){
      memoryExpand(i, es[i]);
    }
    for(i=(0);i<(N);i++){
      es[i] = 0;
    }
    for(i=(0);i<(M);i++){
      addEdgeAdv(n1[i], n2[i], f1[i], f2[i]);
    }
    eps = (T)1e-9;
  }
  void setGraph_w(int N, int M, int n1[], int n2[], T f1[], T f2[], void **mem = wmem){
    int i;
    int j;
    int k;
    node = N;
    for(i=(0);i<(N);i++){
      es[i] = emem[i] = 0;
    }
    for(i=(0);i<(M);i++){
      es[n1[i]]++;
      es[n2[i]]++;
    }
    edge[0] = (int*)(*mem);
    int cTE1_r3A = N;
    for(i=(1);i<(cTE1_r3A);i++){
      edge[i] = edge[i-1] + es[i-1];
    }
    rev[0] = edge[N-1] + es[N-1];
    int RZTsC2BF = N;
    for(i=(1);i<(RZTsC2BF);i++){
      rev[i] = rev[i-1] + es[i-1];
    }
    flow[0] = (T*)(rev[N-1] + es[N-1]);
    int FmcKpFmN = N;
    for(i=(1);i<(FmcKpFmN);i++){
      flow[i] = flow[i-1] + es[i-1];
    }
    *mem = (void*)(flow[N-1] + es[N-1]);
    for(i=(0);i<(N);i++){
      es[i] = 0;
    }
    for(i=(0);i<(M);i++){
      addEdgeAdv(n1[i], n2[i], f1[i], f2[i]);
    }
    eps = (T)1e-9;
  }
}
;
int N;
int A[40];
int B[40];
int main(){
  int i;
  wmem = memarr;
  int node;
  int st;
  int ed;
  maxflow<int,int> f;
  rd(N);N += (-1);
  {
    int Lj4PdHRW;
    for(Lj4PdHRW=(0);Lj4PdHRW<(N);Lj4PdHRW++){
      rd(A[Lj4PdHRW]);
      rd(B[Lj4PdHRW]);
    }
  }
  node = 2*N;
  st = node++;
  ed = node++;
  f.malloc(node);
  f.init(node);
  for(i=(0);i<(N);i++){
    f.addEdge(st, i, A[i]);
  }
  for(i=(0);i<(N);i++){
    f.addEdge(i+N, ed, B[i]);
  }
  for(i=(0);i<(N);i++){
    int j;
    for(j=(0);j<(N);j++){
      if(i!=j){
        f.addEdge(i, j+N, 1073709056);
      }
    }
  }
  wt_L(f.solve(st,ed) + 1);
  wt_L('\n');
  return 0;
}
// cLay varsion 20191006-1

// --- original code ---
// int N, A[40], B[40];
// {
//   int node, st, ed;
//   maxflow<int,int> f;
//   rd(N--,(A,B)(N));
//   node = 2N;
//   st = node++;
//   ed = node++;
//   f.malloc(node);
//   f.init(node);
//   rep(i,N) f.addEdge(st, i, A[i]);
//   rep(i,N) f.addEdge(i+N, ed, B[i]);
//   rep(i,N) rep(j,N) if(i!=j) f.addEdge(i, j+N, int_inf);
//   wt(f.solve(st,ed) + 1);
// }