#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int top = 0, S[1000];
void push(int x) {
  S[++top] = x;
}
int pop(void) {
  top--;
  return S[top+1];
}
int main(void) {
  int a, b;
  top = 0;
  char s[100];
  while(scanf("%s",s) != EOF) {
    if(s[0] == '+') {
      a = pop();
      b = pop();
      push(a + b);
    } else if(s[0] == '-') {
      b = pop();
      a = pop();
      push(a - b);
    } else if(s[0] == '*') {
      a = pop();
      b = pop();
      push(a * b);
    } else {
      push(atoi(s));
    }
  }
  printf("%d\n",pop());
  return 0;
}
