#include<stdio.h>
#include<stdlib.h>
#include<ctype.h>
#include<string.h>
#define MAX 25
int top=-1;
char stack[MAX][MAX];

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

void pop(){
    return stack[top--];
}
int isOperator(char ch){
    return (ch == * ||ch == - || ch == + || ch== / )
}
int isValid(char ch){
    return (isalnum(ch) ||ch == '*' ||ch == '-' || ch == '+' || ch== '/' || ch== '(' ch ==')')
}

void func(char *str){
    int len=strlen(stt),ind;
    for(ind=len;ind>=0;ind--){
        char ch=str[ind];
        if(isValid(ch)){
            printf("Invalid Input");
            return 0;
        }if(isalnum(ch)){
            char temp[2];
            temp[0]=ch;
            temp[1]='\0';
            push(temp);
        }
        else if(isOperator(ch)){
            char ope1[20],ope2[20],res[20];
            strcpy(ope1,pop());
            strcpy(ope2,pop());
            strcpy(res,ope1);
            strcat(res,ope2);
            int l=strlen(res);
            res[l]=ch;
            res[l+1]='\0';
            push(res);
        }
    }
    printf("%s",stack[top]);
}


int main(){
    char ch[MAX];
    if(!scanf("%[^/n]s",ch)){
        printf("Invalid input");
        return 0;
    }
    
    func(ch);
    return 0;
}