#include<stdio.h>
#include<stdlib.h>
#include<ctype.h>
#include<string.h>
#define MAX_SIZE 1000
typedef struct {
    char array[MAX_SIZE];
    int top;
} CharStack;
void initStack(CharStack*stack) {
    stack->top=-1;
}
void push(CharStack* stack,char value) 
{
    if (stack->top<MAX_SIZE-1){
        stack->array[++(stack->top)]=value;
    }
}
char pop(CharStack*stack){
    if(stack->top>=0){
        return
        stack->array[(stack->top)--];
    }
    return'\0';
}
int isEmpty(CharStack*stack){
    return stack->top==-1;
}
int isOperator(char c){
    return c=='+' || c=='-' || c=='*' || c=='/' || c=='^';
}
char*prefixToPstfix(const char*expression) {
    static char result[MAX_SIZE];
    CharStack stack;
    initStack(&stack);
    int j = 0;
    for (int i = strlen(expression)-1;i>=0;i--){
        char c = expression[i];
        if (isspace(c)) {
            continue;
        }
        if (isalnum(c)) {
            push(&stack,c);
        } else if (isOperator(c)) {
            if (stack.top<1) {
                return "Invalid input";
            }
            char op1 = pop(&stack);
            char op2 = pop(&stack);
            result[j++] = op1;
            result[j++] = op2;
            result[j++] = c;
            push(&stack,result[j - 1]);
        } else {
            return "Invalid input";     }
    }
    while (!isEmpty(&stack)) {
        result[j] = '\0';
        for (int k = 0;k < j / 2;k++) {
            char temp = result[k];
            result[k] = result[j - k - 1];
            result[j - k - 1] = temp;
        }
        return result;
    }
    int main() {
        char prefixExpression[MAX_SIZE];
        fgets(prefixExpression,sizeof(prefixExpression),stdin);
        size_t len = strlen(prefixExpression);
        if (len>0 && prefixExpression[len-1]=='\n'){
            prefixExpression[len-1]='\0';
            char*postfixExpression=prefixToPostfix(prefixExpression);
            printf("%s\n",postfixExpression);
            return 0;
        }
    }
}