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

int top, S[1000];

void push(int x) {

S[++top] = x;
}

int pop() {
top--;
rerturn S[top+1];
}

int main() {
int a, b;
top = 0;
char s[100];
 while( scanf("%s", s) != EOF ) {
if ( s[0] == '+7 ) {
a = pop();
b = pop();
push(a + b);
}else if ( s[0] == '-7 ) {
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;
}
