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

void push(int);
int pop(void);

int top = 0;
int S[1000];

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

while(scanf("%s",s) != EOF){

if(s[0] == '-'){
  x = pop();
  y = pop();
  push(y - x); /*注意*/
}

else if(s[0] == '+'){
  x = pop();
  y = pop();
  push(x + y);
}

else if(s[0] == '*'){
  x = pop();
  y = pop();
  push(x * y);
  }

else push(atoi(s));
}

printf("%d\n",pop());

return 0;
}

int pop(void){
if (top == 0) {
  printf("Stack is empty!\n");
  exit(3);
}
  top--;
  return S[top+1];
}

void push(int a){
  if(top == 1000){
    printf("Stack overflow!\n");
    exit(3);
  }
  S[++top] = a;
}

