#pragma GCC optimize ("Ofast")
#include<bits/stdc++.h>
using namespace std;
void *wmem;
char memarr[96000000];
inline int my_getchar_unlocked(){
  static char buf[1048576];
  static int s = 1048576;
  static int e = 1048576;
  if(s == e && e == 1048576){
    e = fread_unlocked(buf, 1, 1048576, stdin);
    s = 0;
  }
  if(s == e){
    return EOF;
  }
  return buf[s++];
}
inline void rd(int &x){
  int k;
  int m=0;
  x=0;
  for(;;){
    k = my_getchar_unlocked();
    if(k=='-'){
      m=1;
      break;
    }
    if('0'<=k&&k<='9'){
      x=k-'0';
      break;
    }
  }
  for(;;){
    k = my_getchar_unlocked();
    if(k<'0'||k>'9'){
      break;
    }
    x=x*10+k-'0';
  }
  if(m){
    x=-x;
  }
}
inline int rd(char c[]){
  int i;
  int sz = 0;
  for(;;){
    i = my_getchar_unlocked();
    if(i!=' '&&i!='\n'&&i!='\r'&&i!='\t'&&i!=EOF){
      break;
    }
  }
  c[sz++] = i;
  for(;;){
    i = my_getchar_unlocked();
    if(i==' '||i=='\n'||i=='\r'||i=='\t'||i==EOF){
      break;
    }
    c[sz++] = i;
  }
  c[sz]='\0';
  return sz;
}
inline void rd(string &x){
  char *buf = (char *)wmem;
  rd(buf);
  x = buf;
}
inline int rd_int(void){
  int x;
  rd(x);
  return x;
}
struct MY_WRITER{
  char buf[1048576];
  int s;
  int e;
  MY_WRITER(){
    s = 0;
    e = 1048576;
  }
  ~MY_WRITER(){
    if(s){
      fwrite_unlocked(buf, 1, s, stdout);
    }
  }
}
;
MY_WRITER MY_WRITER_VAR;
void my_putchar_unlocked(int a){
  if(MY_WRITER_VAR.s == MY_WRITER_VAR.e){
    fwrite_unlocked(MY_WRITER_VAR.buf, 1, MY_WRITER_VAR.s, stdout);
    MY_WRITER_VAR.s = 0;
  }
  MY_WRITER_VAR.buf[MY_WRITER_VAR.s++] = a;
}
inline void wt_L(char a){
  my_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){
    my_putchar_unlocked('-');
  }
  while(s--){
    my_putchar_unlocked(f[s]+'0');
  }
}
string A;
int sz;
int s[100];
int main(){
  int Lj4PdHRW;
  wmem = memarr;
  int KL2GvlyY = rd_int();
  for(Lj4PdHRW=(0);Lj4PdHRW<(KL2GvlyY);Lj4PdHRW++){
    rd(A);
    if(A=="+"){
      sz--;
      s[sz-1] = s[sz-1] + s[sz];
    }
    else if(A=="-"){
      sz--;
      s[sz-1] = s[sz-1] - s[sz];
    }
    else{
      s[sz++] = atoi(A.c_str());
    }
  }
  wt_L(s[0]);
  wt_L('\n');
  return 0;
}
// cLay varsion 20200509-1

// --- original code ---
// string A;
// int sz, s[100];
// {
//   REP(rd_int()){
//     rd(A);
//     if(A=="+"){
//       sz--;
//       s[sz-1] = s[sz-1] + s[sz];
//     } else if(A=="-") {
//       sz--;
//       s[sz-1] = s[sz-1] - s[sz];
//     } else {
//       s[sz++] = atoi(A.c_str());
//     }
//   }
//   wt(s[0]);
// }