#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int stack[100];
int top = 0;
void push(int);
int pop(void);

int main()
{
int x,a,b;
char s[100];

while( scanf("%s", s) != EOF ){
    if ( s[0] == '+' ){
    a=pop();
    b=pop();
    push(a+b);
    } 
    else if ( s[0] == '-' ){
    a=pop();
    b=pop();
    push(b-a);
    } 
    else if ( s[0] == '*' ){
    a=pop();
    b=pop();
    push(a*b);
    } 
    else {
      push(atoi(s));
}
  }
  printf("%d\n",pop());
  return 0;
}

void push(int num)
{
if(top == 100){
    printf("Stack overflow\n");
    exit(2);
}
stack[top] = num;
top++;
}

int pop(void)
{
if(top == 0)
{
    printf("Stack is empty\n");
    exit(3);
}
top--;
return stack[top];
}
