// editor5
#include<stdio.h>
#include<ctype.h>
#include<string.h>
#define MAX 25

char stack[MAX][MAX];
int top = -1;

void push(char ch[]){
    strcpy(stack[++top],ch);
}

char* pop(){
    stack[top--];
}

int isOperator(char ch){
    return (ch=='+'||ch=='-'||ch=='*'||ch=='/');
}
int isValid(char ch){
    return (isalnum(ch) || ch=='+' || ch=='-'||ch=='/'||ch=='('||ch==')');
}

void fun(char *str){
    int len = strlen(str),ind;
    for(ind=len-1;ind>=0;ind--){
        char ch  = str[ind];
        if(isValid(ch)){
            printf("Invalid input");
            
        }
        if(isalnum(ch)){
            char temp[2];
            temp[0] = ch;
            temp[1] = '\0';
            push(temp);
        }
        else if(isOperator(ch)){
            char opd1[MAX],opd2[MAX],res[MAX];
            strcpy(opd1,pop());
            strcpy(opd2,pop());
            strcpy(res,opd1);
            strcat(res,opd2);
            int l = strlen(res);
            res[l] = ch;
            res[l+1] = '\0';
            push(res);
    }
}
int main(){
    char str[MAX];
    scanf("%s",&str);
    fun(str);
    return 0;
}