#include <cstdio>
#include <cstring>
#include <cstdlib>

using bin = int(*)(int, int);
using un  = int(*)(int);

struct {
	int prec;
	bin fn;
} bin_table[256];

struct {
	int prec;
	un fn;
} un_table[256];

const char *src;

bool is_digit(char ch) {
	return ch >= '0' && ch <= '9';
}

int pratt(int prec = 0) {
	int left = 0;

	if (is_digit(*src)) {
		while (is_digit(*src)) {
			left = left*10 + *src - '0';
			src++;
		}
	} else if (un_table[*src].fn != nullptr) {
		char op = *src++;
		left = pratt(un_table[op].prec);
		left = un_table[op].fn(left);
	} else {
		fprintf(stderr, "unknown character: %c\n", *src);
		exit(1);
	}

	while (prec < bin_table[*src].prec) {
		char op = *src++;
		left = bin_table[op].fn(left, pratt(bin_table[op].prec));
	}

	return left;
}

int main(int argc, char **argv) {
    if (argc < 2) {
        printf("usage: pratt expr\n");
        return 1;
    }
    src = argv[1];
	memset(bin_table, 0, sizeof(bin_table));
	memset(un_table, 0, sizeof(un_table));
	un_table['\0'] = {0, nullptr};
	un_table['-'] = {50, [](int a) {return -a;}};
	un_table['+'] = {50, [](int a) {return a;}};
	bin_table['\0'] = {0, nullptr};
	bin_table['+'] = {10, [](int a, int b){return a + b;}};
	bin_table['-'] = {10, [](int a, int b){return a - b;}};
	bin_table['*'] = {20, [](int a, int b){return a * b;}};
	bin_table['/'] = {20, [](int a, int b){return a / b;}};
	bin_table['%'] = {20, [](int a, int b){return a % b;}};
	printf("%d\n", pratt());

	return 0;
}