Replace Bit Field in a 32-bit Register

#include <stdio.h>
#include <stdint.h>

uint32_t replace_field(uint32_t reg, uint32_t val, uint8_t pos, uint8_t len) {
    // Your code here
    uint32_t out=0;
    out=((1<<len)-1)<<pos;
    // out=(1>>pos)|((1<<len)-1);    
    reg &= ~out;
    // printf("%d\n",out);
    return reg |= (val&((1<<len)-1))<<pos;
}

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