Extract a Bit Field from a 32-bit Register

#include <stdio.h>
#include <stdint.h>
//1111000011110000111100001111
uint32_t extract_field(uint32_t reg, uint8_t pos, uint8_t len) {
    // Your code here
    reg = (reg>>pos);
    uint32_t pre =0;
    for(int i =0; i<=len -1 ; i++){
        pre = pre | (1<<i); //0000011111
    }
    reg &= pre;
    return reg;
}

int main() {
    uint32_t reg;
    uint8_t pos, len;
    scanf("%u %hhu %hhu", &reg, &pos, &len);
    printf("%d", extract_field(reg, pos, len));
    return 0;
}