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

long values[64]; int vtop = 0;
char ops[64]; int otop = 0;

int prec(char c) {
  if (c == '+' || c == '-') return 1;
  if (c == '*' || c == '/') return 2;
  return 0;
}

int main() {
  string src;
  printf("Enter expression: ");
  scanf("%s", &src);
  long result = 0;
  for (int i = 0; src[i] != 0; i++) {
    char c = src[i];
    if (c == ' ') continue;
    if (c >= '0' && c <= '9') {
      long v = 0;
      while (src[i] >= '0' && src[i] <= '9') { v = v * 10 + (src[i] - '0'); i++; }
      i--;
      values[vtop++] = v;
    } else if (c == '(') {
      ops[otop++] = c;
    } else if (c == ')') {
      while (otop > 0 && ops[otop - 1] != '(') {
        char op = ops[--otop];
        long b = values[--vtop], a = values[--vtop];
        values[vtop++] = op == '+' ? a + b : op == '-' ? a - b : op == '*' ? a * b : a / b;
      }
      otop--;
    } else if (c == '+' || c == '-' || c == '*' || c == '/') {
      while (otop > 0 && prec(ops[otop - 1]) >= prec(c)) {
        char op = ops[--otop];
        long b = values[--vtop], a = values[--vtop];
        values[vtop++] = op == '+' ? a + b : op == '-' ? a - b : op == '*' ? a * b : a / b;
      }
      ops[otop++] = c;
    }
  }
  while (otop > 0) {
    char op = ops[--otop];
    long b = values[--vtop], a = values[--vtop];
    values[vtop++] = op == '+' ? a + b : op == '-' ? a - b : op == '*' ? a * b : a / b;
  }
  printf("= %ld\n", values[0]);
  return 0;
}